Sinai credited easy monetary policy for the strengthening of the recovery he foresees, saying activity finally is responding to the "happy dust" the central bank dumped on the economy.

"If we're going to err, we need to err on the side of providing too much support to the economy than too little," added Mark Zandi, chief economist at Moody's Analytics Inc. in West Chester, Pennsylvania.

At the start of last year, the economy also looked as if it was taking off, with payrolls rising by 827,000 in the first four months of 2011. It then was hit by a series of shocks: higher oil prices triggered by the Arab Spring uprisings, an earthquake in Japan, continued turmoil in the euro region and the debt ceiling standoff in the U.S.

GDP ended up rising 1.7 percent in 2011, below the 3.1 percent median forecast of private economists surveyed by Bloomberg at the start of last year and 3 percent in 2010.

Fed policy makers also proved to be too optimistic. In January 2011, they were looking for growth of 3.4 percent to 3.9 percent for the year. Bernanke in November blamed the shortfall in part on "some elements of bad luck."

The risk is the U.S. could suffer a similar fate this year. The escalation of tensions with Iran over the Mideast nation's nuclear program probably has added a premium of about $5 to $10 a barrel to oil prices, according to Robert McNally, a former White House official under President George W. Bush and president of the Rapidan Group in Bethesda, Maryland.

Higher Oil Prices

That could go higher, McNally said in a report last month for the Council on Foreign Relations in New York. Crude for March delivery settled at $98.67 a barrel on Feb. 10 on the New York Mercantile Exchange.

Meanwhile, European policy makers struggle to contain the region's sovereign-debt crisis, and U.S. lawmakers remain at odds over fiscal policy. The economy would suffer a "significant blow" if Congress fails to extend a payroll-tax cut and unemployment assistance that are scheduled to expire on Feb. 29, Zandi said.

"I would be very enthusiastic about recent economic data if we hadn't had last year's experience," he said.