Citigroup shares tumble despite Alwaleed move

* Shares fall to 1994 level, cost to insure debt rises

* Alwaleed to raise stake to 5 percent

* Citigroup said among final bidders for Chevy Chase Bank

(Adds comments on bank's business, government aid)

By Jonathan Stempel and Dan Wilchins

NEW YORK (Reuters) - Citigroup Inc (C.N) lost more than one-quarter of its market value as new support from its largest individual investor failed to ease worries over whether it will have enough capital to withstand billions of dollars of potential losses.

Saudi Prince Alwaleed bin Talal said he plans to increase his stake in Citigroup, the No. 2 U.S. bank by assets, to 5 percent from less than 4 percent, calling its shares "dramatically undervalued."

Alwaleed expressed "full and complete support" for bank management, including Chief Executive Vikram Pandit, who said this week the bank will slash 52,000 jobs and 20 percent of expenses.

Investors drove the bank's shares down below $5 on Thursday, a level not seen since 1994. Some investors and analysts questioned whether Citigroup would be able to handle billions of dollars in potential credit losses and writedowns in 2009 as the world economy sinks into recession.

Some investors have said the government might have to step in, perhaps augmenting the $25 billion it injected last month as part of a $700 billion rescue package.

Citigroup is not seeking any government financial aid, a person close to the bank said, adding that the bank was not seeing any unusual business activity.

Citigroup could face more than $20 billion in losses in 2009 on commercial real estate, credit cards and emerging markets, analysts said.

"How much capital is Citi going to need?" said Keith Davis, a bank analyst at Farr, Miller & Washington in Washington, D.C. "I don't think anyone knows, and so the knee-jerk reaction is to sell first and ask questions later."

Citigroup shares closed down $1.69, or 26.4 percent, at $4.71, with volume topping 721 million shares. The stock is down 50.5 percent this week.

A Citigroup spokeswoman declined to comment on the share price.

JPMorgan Chase & Co (JPM.N) closed off 17.9 percent, and Bank of America Corp (BAC.N) down 13.9 percent. Along with Citigroup, the banks are components of the Dow Jones industrial average .DJI, which shed 5.6 percent.

JPMorgan is cutting about 3,000 investment banking jobs, or 10 percent of that unit, to cope with the deteriorating economy, people familiar with the matter said.

Separately, KeyCorp (KEY.N), a Midwest regional bank, reduced its common stock dividend for the second time in six months.

STABILITY 'TOP PRIORITY'

Citigroup's market value, which once topped $270 billion, fell to $25.7 billion on Thursday. The bank was overtaken in market value this week by U.S. Bancorp (USB.N) and Bank of New York Mellon Corp (BK.N), despite being more than four times larger by assets than those companies combined.

Five-year credit default swaps for Citigroup rose to 395 basis points, meaning it would cost $395,000 annually to protect $10 million of debt, according to Phoenix Partners Group. That's up from $357,000 of annual payments on Wednesday, according to Markit.

Earlier this year, the government has rescued giant insurer American International Group Inc (AIG.N) and mortgage giants Fannie Mae (FNM.N) Freddie Mac (FRE.N).

Citigroup "will get bailed out, and that's another unfortunate strain on the U.S. government," said Saj Karim, an investment adviser at Cannacord Capital in Waterloo, Ontario.

U.S. Treasury Secretary Henry Paulson declined to comment on Citigroup.

Despite its troubles, Citigroup is one of three final bidders, along with JPMorgan and Capital One Financial Corp (COF.N) for Chevy Chase Bank, a Bethesda, Maryland, lender with $11.4 billion in deposits, sources said.

Pandit suffered a setback last month when Wells Fargo & Co (WFC.N) agreed to buy Wachovia Corp WB.N, trumping Citigroup's bid to buy much of the Charlotte, North Carolina-based bank and add $418.8 billion of deposits.

'LONG-TERM WINNER'

Alwaleed said the bank is "taking all the necessary steps to position the company to withstand the challenges facing the banking industry and the global economy."

The Saudi billionaire, a nephew of Saudi King Abdullah, said he is "fully confident that Citigroup's universal banking model and global franchise will make it a long-term winner in the financial services industry."

The percentage of the prince's stake in the bank fell in late 2007 and early 2008 as Citigroup raised some $50 billion in capital from sovereign wealth funds and other investors, including Alwaleed, to shore up its balance sheet. The $25 billion government injection is in addition to this amount.

Alwaleed also came to the bank's aid in 1991, when he invested $590 million in Citigroup predecessor Citicorp, which at the time needed cash as it struggled with Latin American loan losses and a collapse in U.S. real estate prices.

LIQUIDITY

Citigroup shares lost one-third of their value in the first three days of this week as investors worried that Pandit's cost-cutting plans would not restore the bank to health.

Citigroup has lost $20.3 billion in the last year and taken tens of billions of dollars in writedowns on mortgage and other toxic debt. Analysts expect it to lose money in the fourth quarter, and some don't see any profit in 2009.

"We don't see anything wrong from the point of view of liquidity," said Standard & Poor's credit analyst Tanya Azarchs. "We can see a fourth-quarter loss that could be getting worse because of events in the marketplace, but they are not alone."

Citigroup's potential losses could include a write-down tied to ailing bond insurer Ambac Financial Group Inc (ABK.N), which said Wednesday it ended two insurance contracts on collateralized debt obligations, paying 28 cents on the dollar. That could imply a $2 billion writedown at Citigroup.

(Additional reporting by Elinor Comlay, Kristina Cooke and Jonathan Spicer in New York; Gina Keating in Simi Valley, California; and Emily Kaiser in Washington, D.C.; writing by Christian Plumb and Jonathan Stempel; editing by John Wallace and Jeffrey Benkoe)