Officials at the Federal Reserve Bank said Tuesday that the economy’s outlook has improved since March but still expect weakness for some time.

The Fed’s policy-making arm, Federal Open Market Committee, said in a statement today that it will keep its key interest between 0 to 0.25 percent, saying that conditions will require “exceptionally low” rates for some time.

Assessing the economy, the FOMC, said it has shown some signs of stability, saying the rate of contraction “appears to be somewhat slower.”

“Although the economic outlook has improved modestly since the March meeting, partly reflecting some easing of financial market conditions, economic activity is likely to remain weak for a time,” the committee said.

The committee showed concern about low inflation, saying that it “could persist for a time below rates that best foster economic growth and price stability in the longer term.”

The Fed also said it will buy up to $300 billion of Treasury securities by autumn.