The US Federal Reserve is leaving its key interest rate unchanged but signalling that it's prepared to start cutting rates if needed to protect the US economy from trade conflicts and other threats.

The Fed left its benchmark rate — which influences many consumer and business loans — in a range of 2.25 percent to 2.5 percent, where it's been since December.

While not changing rates, Fed officials say that uncertainties "have increased" and for that reason, the central bank was prepared to "act as appropriate to sustain the expansion."

That language echoes comments Fed chairman Jerome Powell made two weeks ago that triggered a huge stock market rally as investors started believing rate cuts are on the way. As expected the Fed removed a pledge to be "patient" in changing rates.

A survey of the 17 Fed officials showed that nearly half now expect at least one rate cut this year, with seven projecting two cuts. At the March meeting, no officials had forecast a rate cut.