In fact, it's likely to be more costly than the $34 billion that the Big Three were asking for last week.

Congressional leaders and the White House were working Tuesday to finalize details of a $15 billion loan designed to get the two most troubled automakers, General Motors (GM, Fortune 500) and Chrysler LLC, through March without running out of cash.

Still, that is only seen as a stopgap measure to keep the companies rolling until the new Congress and the Obama administration can consider the full request from GM, Chrysler and Ford Motor (F, Fortune 500) early next year.

And even the automakers admit that they are going to need a lot more than $34 billion to remain viable.

Executives of all three companies have said they still hope to get at least $20 billion of the $25 billion in federal loans over the next three years from the Energy Department. Those loans have already been approved to help them build more fuel efficient vehicles.

The $15 billion being considered for the current bailout would come out of that $25 billion. Democrats in Congress plan on replenishing those funds early next year.

But Big Three executives are already on record as wanting to see Congress boost the size of the Energy Department loans to $50 billion sometime next year.

Each of the automakers also hope to have their finance operations tap into the $700 billion set aside by Congress in October to help Wall Street firms and banks.

GMAC, the finance arm owned 49% by GM, has filed to become a bank holding company, while Ford and Chrysler have filed to become industrial loan companies, which could also open up that source of funds.

Those funds would go to help provide credit to dealerships and consumers that the automakers say they need to support sales. The amount of money to be requested from those funds is not yet known.

The automakers are also seeking help from the Canadian government, where all three operate plants. A report in the Hamilton Spectator estimates that the U.S. automakers are seeking more than $5 billion in loans from the Canadian government. The U.S. automakers could not confirm this.

But even all these additional sources of capital may not be enough to keep the industry out of bankruptcy.

The automakers came up with the $34 billion request based on expectations of a modest rebound in auto sales in December and the first quarter of 2009. If that doesn't materialize, the cost of saving the industry would certainly rise.

Last week, Moody's Economy.com economist Mark Zandi suggested during one of the auto bailout hearings on Capitol Hill that the Big Three could need between $75 billion to $125 billion over the next two years if they are to survive.

He predicted that even if the government approves the $34 billion loan package, the automakers would be back to Washington later in 2009 asking for additional help.

That's because he thinks U.S. auto sales will remain weak well into 2010, due to problems in the economy and the bubble in auto sales from earlier in the decade.

In his testimony, Zandi said he estimates the entire auto industry would have to shut down production for nearly a year to work off the excess cars and light trucks that were sold during the bubble years.

With that in mind, Zandi said in an interview this week that his estimates for how much cash the industry needs might be low since it doesn't account for the lower revenue the Big Three are likely to receive if consumers continue to shun more expensive SUVs and pickups in favor of smaller, cheaper car models with better fuel efficiency.

Other experts agree that coming up with the actual amount that will be needed to save Detroit is difficult, but that Zandi's $75 billion to $125 billion estimate is probably closer to reality than $34 billion.

"You have to wonder if the initial cost estimates are anywhere near what the final costs are going to be," said Bob Schnorbus, chief economist with J.D. Power & Associates. "It'll take terrific management skills to contain it to $34 billion."

J.D. Power & Associates has already cut forecasts several times and will soon issue another sharp reduction to its current 2009 industrywide U.S. sales forecast of 12.6 million cars and light trucks. The firm said its new forecast is expected to be closer to annual sales of 11 million.

That's well below the targets set by General Motors and Ford Motor when they submitted their turnaround plans to Congress last week.

GM estimated industrywide sales of just under 12 million cars and light trucks for 2009 while Ford predicted sales of just over 12 million. Each said their need for federal help would increase if sales fell short of those forecasts.

Chrysler presented a more conservative estimate of 11.1 million vehicles sold industrywide next year.

And the worse the sales outlook gets, the more costly it will become for the Big Three to adjust to the weaker sales environment by reducing capacity. The cost of buyouts tied to plant and dealership closings could easily be more than $1 billion, according to some industry experts.

"If you want to accelerate cost savings or dealership reductions or brand elimination, all that requires incremental cash in addition to what's being used in the ongoing operations," said Robert Schulz, senior auto credit analyst for Standard & Poor's. "It can be more expensive in the short run to better position yourself for the long run." 

NEW YORK (CNNMoney.com) -- Stocks retreated Tuesday, led by financial, retail and transportation shares as investors bailed out of a variety of stocks after the recent retreat.

The Dow Jones industrial average (INDU) slumped 240 points or 2.7%. The Standard & Poor's 500 (SPX) index lost 2.3% and the Nasdaq composite (COMP) lost 1.6%.

Stocks had been on both sides of unchanged through the session as investors digested the day's batch of negative corporate news and kept an eye on the latest news on a potential automaker loan package. But stocks turned decidedly negative in the afternoon.

An agreement on a loan package for the auto industry had been expected late Monday. But lawmakers were still debating the details Tuesday, with a package now expected later today or Wednesday.

The back-and-forth was perhaps causing some of the stock weakness Tuesday, with investors eager to see a resolution, said Ron Kiddoo, chief investment officer at Cozad Asset Management.

"The automaker talk is part of it, but really we've had some pretty good moves off that Nov. 20 low and so people are taking a breather," he said.

Since hitting the most recent bear market lows on Nov. 20, stocks, as represented by the S&P 500, had risen 21% through Monday's close.

Monday was a big day on Wall Street, with all three major gauges gaining at least 3.5% in response to President-elect Barack Obama's plan to create 2.5 million jobs by 2011 and reports that a bailout for the automakers is en route.

Company news: Package-delivery firm FedEx (FDX, Fortune 500) warned late Monday that fiscal 2009 earnings won't meet earlier forecasts due to the impact of the slowing economy. Shares lost 14.5%. Competitor UPS (UPS, Fortune 500) slipped 7%.

Both stocks were also under pressure after ratings agency Fitch and brokerage JPMorgan Chase said truckers will be hit hard in 2009 because of the recession. Although a variety of transportation companies will feel the impact of the slowdown, railroads are in better shape to withstand the retreat, Fitch said.

Con-way (CNW), YRC Worldwide (YRCW, Fortune 500) and JB Hunt Transport Services (JBHT) were among the trucker stocks declining.

The Dow Jones Transportation (DJTA) average fell 5.6%. The transports rallied Monday on Obama's plans to modernize buildings and revamp roads.

Sony (SNE) said it is cutting 8,000 jobs worldwide as part of a plan to cut costs by $1.1 billion. Shares gained 2%.

Other companies announcing job cuts included software maker Novellus (NVLS), manufacturer Danaher (DHR, Fortune 500) and the Wyndham Hotel Group (WYN).

In total, the four companies announced around 14,000 in job cuts.

Walt Disney (DIS, Fortune 500) said bookings at its hotels and theme parks have improved, thanks to discounts, but ad sales remain weak. Shares lost 5.6%.

Texas Instruments (TXN, Fortune 500) warned late Monday that current-quarter earnings and sales won't meet earlier forecasts. Fellow chipmakers Broadcom (BRCM) and Altera (ALTR) also warned Monday that fiscal fourth-quarter sales won't meet forecasts.

And chipmaker National Semiconductor (NSM) reported a big drop in fiscal second-quarter sales and warned that current-quarter revenue would drop from the previous quarter.

Despite the news, all four chip stocks gained Monday.

Market breadth was negative. On the New York Stock Exchange, losers topped winners by over two to one on volume of 1.44 billion shares. On the Nasdaq, decliners topped advancers two to one on volume of 2.32 billion shares.

Automakers: Lawmakers continue to debate a $15 billion loan package for GM and Chrysler that would keep the automakers from declaring bankruptcy. The plan would be something of a stopgap measure that would tide the automakers over in order for the new Congress and incoming Obama administration to come up with a longer-term plan for the industry.

Wall Street economists and other market pros are worried that the failure of any one of the Big Three could trigger massive job losses and send the U.S. deeper into recession. (Full story)

GM (GM, Fortune 500) shares fell 4.7%, while Ford Motor (F, Fortune 500) lost 4%.

The U.S. has officially been in a recession since December 2007, with the collapse of the housing market and subsequent credit crisis causing the economy to weaken and consumer spending to wither.

Tuesday brought one piece of economic news that was not as weak as had been expected. A report showed that October pending home sales fell 0.7% from the previous month versus forecasts for a drop of 3%.

Bonds: Treasury prices gained, lowering the yield on the benchmark 10-year note to 2.63 from 2.74% late Monday. The 10-year yield dipped below 3% last month for the first time since the note was first issued in 1962. Treasury prices and yields move in opposite directions.

Lending rates improved modestly. The 3-month Libor rate slipped to 2.16% from 2.19% Monday, according to Bloomberg. The overnight Libor fell to a new record low of 0.14% from 0.19% Monday. Libor is a key bank lending rate.

Other markets: The dollar declined versus the yen and gained against the euro.

U.S. light crude oil for January delivery fell $1.64 to settle at $42.07 a barrel, after ending the previous session at a four-year low.

COMEX gold for February delivery jumped $4.90 to settle at $774.20 an ounce.

Gasoline continued its fall to nearly four-year lows, with prices down 1.8 cents to a national average of $1.698 a gallon, according to a survey of credit-card swipes released Tuesday by motorist group AAA. Prices have been sliding for 2-1/2 months and have dropped more than $2 a gallon, or 56%.