FILE PHOTO: Federal Reserve Board building on Constitution Avenue is pictured in Washington, U.S., March 19, 2019. REUTERS/Leah Millis -/File Photo

(Reuters) - The Federal Reserve’s balance sheet increased to a record $6.42 trillion this week as the central bank used its nearly unlimited buying power to soak up assets to keep markets functioning amid an abrupt economic free fall due to the coronavirus pandemic.

Since early March, the Fed has slashed interest rates to zero, restarted bond purchases and rolled out an unprecedented range of programs to keep credit flowing and shore up business and household confidence.

The central bank’s balance sheet as of Wednesday rose nearly $300 billion from $6.13 trillion a week earlier. That is up from just $4.29 trillion in the first week of March.

It is now the equivalent of roughly 30% of the size of the U.S. economy before the crisis struck, and will certainly grow larger in the weeks ahead as the Fed keeps piling on assets and the economy shrinks.

The central bank continued to snap up Treasury securities, mortgage bonds and other assets, according to data released on Thursday. The Fed’s holdings of mortgage-backed securities rose to $1.57 trillion from $1.46 trillion. Treasury holdings rose to $3.79 trillion from $3.63 trillion.

Use of the Fed’s central bank liquidity swap lines, which allow foreign central banks to exchange their local currencies for dollars, rose to $378.3 billion on Wednesday from $358.1 billion the previous week.

Loan balances for the Fed’s discount window, its last-resort lending program for banks, fell to $36.3 billion from $43.45 billion a week ago.

Loans with the Fed’s primary dealer credit facility edged up to $33.4 billion from $33 billion the previous week. Use of the money market mutual fund liquidity facility slipped to $50.7 billion from $53.2 billion the week before.

Thursday’s report gave the first indication of usage of the Fed’s newest support facility. The Commercial Paper Funding Facility II LLC, a special-purpose vehicle set up by the Fed with seed money from the U.S. Treasury, reported holdings of $974 million as of April 15. The facility began operations on Tuesday.