It is just one big headline grabbing gesture after another. It is as if the External relations department was making monetary policy.

WASHINGTON — Hoping to avoid a systemic meltdown in financial markets, the Federal Reserve on Sunday approved a $30 billion credit line to engineer the takeover of Bear Stearns and announced an open-ended lending program for the biggest investment firms on Wall Street.

In a third move aimed at helping banks and thrifts, the Fed also lowered the rate for borrowing from its so-called discount window by a quarter of a percentage point, to 3.25 percent.

The moves amounted to a sweeping and apparently unprecedented attempt by the Federal Reserve to rescue the nation’s financial markets from what officials feared could be a chain reaction of defaults.

After a weekend of intense negotiations, the Federal Reserve approved a $30 billion credit line to help JPMorgan Chase acquire Bear Stearns, one of the biggest firms on Wall Street, which had been teetering near collapse because of its deepening losses in the mortgage market.

In a highly unusual maneuver, Fed officials said they would secure the loan by effectively taking over the huge Bear Stearns portfolio and exercising control over all major decisions in order to minimize the central bank’s own risk.