Dallas Federal Reserve President Richard Fisher said the timing of monetary tightening will depend on conditions in the U.S. economy, which will slow in the latter half of this year, Japan's Nikkei newspaper reported on Tuesday.

Weakness in private consumption may hurt growth and politicians might call for an expansion of monetary easing, although there is little more the Fed can do, Fisher said in an interview with the economic daily.

But Richmond Fed President Jeffrey Lacker was more optimistic, telling the Nikkei that private consumption and corporate capital investment will expand enough to keep the U.S. economy on a sustained recovery later this year and through next year.

Europe's credit problems were unlikely to severely hurt the U.S. economy, with the impact on real GDP growth likely to be around 0.1 percent to 0.2 percent, he said.

With the U.S. recovery sustained, the key would be whether to drop the U.S. central bank's promise to keep interest rates low for an "extended period" late this year, Lacker said.