LONDON, Nov 10 (Reuters) - The United States' economy is not robust enough yet and unemployment is too high for policymakers to begin to withdraw stimulus, Boston Fed President Eric Rosengren said on Tuesday.

It's a question of timing, Rosengren said in response to a question about exit strategies. We're not there yet.

Rosengren said there were various options for withdrawing stimulus - including raising interest rates, using reverse repos and selling back the securities that had been bought.

There are plenty of options. I don't think it's a case of whether we have the tools, he said. It's really a question of what would be the most effective tool and when for the economy is the appropriate time to raise rates.

Rosengren said unemployment, running at a 26-year high of 10.2 percent, was roughly double where he expected the natural rate to be.

What you want is an interest rate path that will generate an outcome that over a few years will get you back to full employment and you would hope to have inflation at 2 percent, he said.

Rosengren is not a voting member on the policy-setting Federal Open Market Committee this year. He will vote in 2010.

(Reporting by Christina Fincher and Nigel Davies; Editing by Ron Askew)