TIMELINE: Fed actions to boost liquidity

CHICAGO (Reuters) - The Federal Reserve is mulling additional steps to tackle liquidity problems in financial markets, in case measures taken to date fail to gain traction, a Fed official said on Wednesday.

The moves would be the latest in a string of extraordinary moves taken by the Fed in an effort to prevent a credit crisis triggered by rising mortgage defaults from swamping the financial system and the U.S. economy.

The Fed is considering a plan in which the Treasury Department would borrow in excess of its requirements and deposit the surplus at the Fed. The central bank is also considering whether to issue debt under the Fed's name and seek authority to immediately pay interest on commercial bank reserves.

Following are previous extraordinary steps the Fed has taken since August, when the credit crisis erupted:

March 24: Fed details its role in amended JPMorgan Chase & Co's (JPM.N: Quote, Profile, Research, Stock Buzz) planned purchase of ailing investment bank Bear Stearns Cos BSC.N. It says it will assume control of a portfolio of Bear Stearns assets valued at $30 billion, pledged as security. Any profit from the assets will accrue to the Fed, while JPMorgan will bear the first $1 billion of any losses. The Fed will finance the remaining $29 billion on a non-recourse basis to JPMorgan.

March 16: The Fed in a surprise move cuts the discount rate it charges on direct loans to banks and announces new lending program to provide credit to other big Wall Street firms. In addition, it increases the maximum maturity of discount rate loans to 90 days from 30 days. The actions are taken in concert with a decision to approve special financing to facilitate the purchase of Bear Stearns by JPMorgan Chase.

March 14: The Fed says it authorized JPMorgan Chase to borrow at the discount window on behalf of Bear Stearns, an emergency move last used in the Great Depression.

March 11: The Fed says it will accept a broader range of collateral, including home mortgages, in a new securities lending program. It says it would lend up to $200 billion to primary dealers, secured for 28 days, and accept federal agency home mortgage-backed securities and highly rated private mortgage-backed securities as collateral.

The action was coordinated with steps by the Bank of Canada, Bank of England, European Central Bank and Swiss National Bank. The Fed also says it increased existing currency swap lines with the ECB and SNB to up to $30 billion and $6 billion, respectively, and extended the term of those lines through September to help those central banks provide dollar liquidity in their markets.