The president's top economic advisers are pledging to work with their counterparts around the world to restore confidence and stability to financial markets roiled by tight credit and worries about a global economic slowdown .

The President's Working Group on Financial Markets said in a statement Monday it planned to quickly implement the expanded authorities granted to federal regulators by the $700 billion rescue package passed on Friday. The working group was formed after the 1987 stock market crash.

The group, which includes Treasury Secretary Henry Paulson and Federal Reserve Chairman Ben Bernanke, said it planned to move "with substantial force on a number of fronts."

To that end, the administration was expected to announce shortly that it had tapped a 35-year-old former Goldman Sachs executive to head the government's rescue effort on an interim basis, according to an official who asked not to be named.

The working group's statement was one of a number of rapid-fire announcements released early Monday before Wall Street stocks began trading. Stocks tumbled after the opening, joining a sell-off around the world as fears grew that the financial crisis will cascade through economies globally despite bailout efforts by the U.S. and other governments.

European governments took steps to limit the damage from the growing global financial crisis. Among other things, the governments of Germany, Ireland, Greece and Denmark said they would guarantee bank deposits.

In a fresh effort to loosen dangerous credit clogs, the Federal Reserve said it will significantly expand its loan program to squeezed banks, increasing one program to as much as $900 billion by the end of this year.

The Fed also said it will begin paying interest on commercial banks' reserves, another way to expand the Fed's resources to battle the worst credit crisis in decades.

Congress in the $700 billion bailout bill President Bush signed on Friday gave the Fed the power to pay interest on those reserves for the first time. The law accelerated the effective date to October of this year versus in 2011. That will encourage banks to keep more resources at the central bank.

Treasury said Monday that it would expand the size of its upcoming debt auctions to handle the increased borrowing needs to fund the $700 billion bailout effort, which is expected to buy about $50 billion in troubled assets each month. Treasury said it was considering bringing back the three-year note besides expanding the size of other debt auctions.

Meanwhile, the official — who spoke on condition of anonymity because the announcement had not been made public — said Neel Kashkari, 35, an assistant Treasury secretary for international affairs, had been selected to head Treasury's new Office of Financial Stability, which was created by the $700 billion bailout legislation. Kashkari helped draft the legislation as one of Paulson's close adviser on the crisis. Kashkari joined the government after working at Goldman Sachs, the firm Paulson headed before joining the Bush administration in 2006.

The statement from the president's working group laid out a number of initiatives that the Treasury, the Fed and other government regulators including the Federal Deposit Insurance Corp. would be undertaking.

"The diversity of institutions and markets under stress, and the magnitude and complexity of the adjustment under way, requires that the tools available to policymakers, regulators and supervisors be used in forceful and coordinated ways across regulatory and supervisory agencies in the United States and throughout the world," the working group said in its statement.

Over the weekend, governments across Europe rushed to prop up failing banks. The German government and financial industry agreed on a $68 billion bailout for commercial-property lender Hypo Real Estate Holding AG, while France's BNP Paribas agreed to acquire a 75 percent stake in Fortis' Belgium bank after a government rescue failed.

The Dow Jones industrials skidded more than 500 points in morning trading and fell below 10,000 for the first time in four years, while the credit markets remained under strain.

Global markets sold off, too. Tokyo's Nikkei 225 index fell to its lowest level in 4 1/2 years, sinking 4.25 percent to 10,473.09. Hong Kong's Hang Seng index slid 5 percent to 16,803.76. Markets in mainland China, Australia, South Korea, India, Singapore and Thailand also dropped sharply.

By midafternoon Europe time, Britain's benchmark stock index, the FTSE 100, lost 245.70 to 4,734.55 — a 4.93 percent fall. Germany's DAX index fell 5.23 percent to 5,493.95. France's CAC-40 index dropped 5.59 percent to 3,852.63.

Broader indexes also tumbled. The Standard & Poor's 500 index shed 5.42 percent, Nasdaq composite index fell 5.57 percent, and The Russell 2000 index of smaller companies dropped 4.53 percent.

The anxiety was again obvious in the credit markets. The yield on the three-month Treasury bill slipped to 0.40 percent from 0.50 percent late Friday. Demand for bills remains high because of their safety; investors are willing to take extremely low returns just to have their money in a secure place.