The Federal Reserve's balance sheet increased to a record 6.62 trillion U.S. dollars 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 about 200 billion U.S. dollars from 6.42 trillion U.S. dollars a week earlier. That is up from just 4.29 trillion U.S. dollars in the first week of March.

It is now the equivalent of roughly 30 percent 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 1.62 trillion U.S. dollars from 1.57 trillion U.S. dollars. Treasury holdings rose to 3.91 trillion U.S. dollars from 3.79 trillion U.S. dollars.

Use of the Fed's central bank liquidity swap lines, which allow foreign central banks to exchange their local currencies for dollars, rose to 409.7 billion U.S. dollars on Wednesday from 378.3 billion U.S. dollars the previous week.

Loan balances for the Fed's discount window, its last-resort lending program for banks, fell to 33.7 billion U.S. dollars from 36.3 billion U.S. dollars a week ago.

Loans with the Fed's primary dealer credit facility dipped to 31.5 billion U.S. dollars from 33.4 billion U.S. dollars the previous week. The use of the money market mutual fund liquidity facility slipped to 48.8 billion U.S. dollars from 50.7 billion U.S. dollars the week before.

The Commercial Paper Funding Facility II LLC, a special-purpose vehicle set up by the Fed with seed money from the U.S. Treasury, rose to 2.7 billion U.S. dollars from 974 million U.S. dollars on April 15. That facility began operations last week.

The newest item appearing on the Fed's balance sheet was loans that have taken on from banks participating in the Small Business Administration's "Payroll Protection Program," initially rolled out at 349 billion U.S. dollars but set to be expanded under new appropriations from Congress after the original amount ran out in less than two weeks. The Fed held just over eight billion U.S. dollars of PPP loans as of Wednesday, an amount certain to rise in the coming weeks.

The Fed also said it will shortly announce new rules to expand access to the PPP beyond banks so that a broader set of institutions can participate.