The lone Federal Reserve policymaker to dissent against the U.S. central bank's decision this week to end its bond-buying stimulus said Friday that the Fed was risking its credibility by failing to take action against a worrisome drop in inflation.

Not only is there no evidence that inflation is moving back toward the Fed's 2-percent goal, Minneapolis Fed President Narayana Kocherlakota said in a statement explaining his dissent, the outlook for inflation is "arguably worse" than it was last December.

That is when the Fed began paring its monthly bond purchases, a wind-down that it completed on Oct. 29 when the Fed wrapped up its two-day meeting.

"Failing to act in response to this subdued inflation outlook increases the downside risk to the credibility of our 2 percent inflation target," Kocherlakota said. "As we have seen in Japan and may now be seeing in Europe, the credibility of central bank inflation targets cannot be taken for granted."

The Bank of Japan earlier Friday shocked markets by ramping up its own bond-buying stimulus, a move BOJ chief Haruhiko Kuroda said showed "unwavering determination" to defeat the deflation that has sapped Japan's economy for years. The European Central Bank has also struggled with the specter of a sagging inflation outlook amid slowing growth.

The weak global backdrop has complicated the task ahead for the Fed, potentially hampering the U.S. recovery and undercutting the Fed's effort to move inflation higher. Fresh U.S. data Friday underscored the crosscurrents in the domestic economy, with wages growing at their strongest pace since 2008, but the Fed's preferred gauge of inflation registering just 1.5 percent.

For now, however, the Fed has signaled growing confidence in its economic outlook, saying Wednesday that U.S. labor market slack is "diminishing" and downplaying the recent slowdown in inflation as driven by a drop in energy prices that is likely to be temporary.

Kocherlakota, for his part, said the Fed could have continued to buy bonds at a pace of $15 billion a month, or committed to keeping interest rates near zero until the outlook for the inflation one to two years ahead had risen to 2 percent.

"These actions would have put upward pressure on the demand for goods and services and on prices," Kocherlakota said. "Just as importantly, these actions would have communicated that the Committee is determined to do what it takes to push inflation back to 2 percent as rapidly as is possible."

Separately, San Francisco Fed President John Williams, speaking in South Africa, suggested he too is focused on more effective ways to boost inflation towards the Fed's 2-percent target, discussing two controversial approaches advocated at various times by both Kocherlakota and fellow policy dove Charles Evans of the Chicago Fed. Williams, however, was careful to say he did not necessarily advocate either.