Very accommodative Federal Reserve monetary policy will stay for an extended period and a premature exit from this strategy could thwart U.S. economic recovery, a top Fed official said on Tuesday.

But St. Louis Federal Reserve Bank President James Bullard said having a plan to withdraw the Fed's massive expansion of the U.S. monetary base was important to control inflation expectations. And he said that selling Fed-owned assets was probably the most likely way it would choose to go.

Without an exit strategy, expectations of high inflation may develop, Bullard told a Global Interdependence Center event held at the Federal Reserve Bank of Philadelphia.

If expectations of inflation feed into today's long-term yields, those yields will rise today and hamper recovery prospects, he said in prepared remarks.

Bullard will be a voting member of the Fed's policy-setting committee next year.

The Fed has cut interest rates to almost zero and pledged to buy up to $1.75 trillion worth of U.S. government and mortgage debt to combat a severe recession and prevent the economy from slipping into a Japan-style deflation, which inflicted a decade of stagnation on that country in the 1990s.

Bullard, in remarks used in a powerpoint presentation to illustrate his argument, said there were various ways that the Fed could reduce its balance sheet to tighten policy.

But he said two options -- the issuance of Treasury supplementary financing programs or the issuance of Fed debt -- were unlikely because of the size of the U.S. budget deficit.

Other options involving repurchase programs and the payment by the Fed of interest on reserves were untested in the context that the U.S. central bank now faces, Bullard said.

Selling assets as appropriate is the most likely option, he said.

(Reporting by Alister Bull; Editing by Chizu Nomiyama)