WASHINGTON — Turmoil in international credit markets posed such a risk to the U.S. economy in mid-September that a sharp, half-point interest rate cut was the "most prudent course of action," according to the Federal Reserve.

Minutes of a Sept. 18 meeting, at which the Fed cut its target for a key short-term interest rate to 4.75 percent, show Fed officials united on the move to "forestall some of the adverse effects on the economy that might otherwise arise."

The Fed was unsure what was ahead, however, emphasizing that policy hinged on the economy's performance.

The minutes, released yesterday, helped the Dow Jones industrial average and Standard & Poor's 500 index rally to record highs.

The Fed decided not to issue a highly explicit statement of economic risks after the meeting, "as such a characterization could give the mistaken impression that the committee was more certain about the economic outlook than was, in fact, the case," the minutes said.

"Future actions would depend on how economic prospects were affected by evolving market developments and by other factors," according to the minutes.

With inflation easing, and the economy likely to slow, Fed officials said the rate cut didn't appear to pose a major threat of accelerating price pressures — though adding they remained vigilant on inflation.