Most economists at Wall Street's top financial institutions expect the Federal Reserve in 2013 to end the program with which it bought Treasury debt in an effort to stimulate the economy, according to a Reuters poll on Friday.

Economists at nine of 16 primary dealers -- the large financial institutions that do business directly with the Fed -- said they expect the current Fed program of buying $45 billion per month of Treasuries to end in 2013.

Of the nine, eight said the central bank would quit the program in the fourth quarter or the end of the year. One forecast the end of the program in June.

Six of 15 economists at primary dealers said the Treasury purchase program would close in 2014, while one said it would continue through to the first half of 2016.

Minutes from the Fed's December policy meeting, released on Thursday, showed "several" top officials expected to slow or stop the so-called quantitative easing program "well before" the end of the year. That news surprised some on Wall Street and prompted a drop in stocks and bonds, and a rise in the dollar.

"It is hard to be as confident of the purchases continuing at the same pace, because we had originally thought they were going to last through the fourth quarter of 2014, but now it is not as clear that is going to be the case," said Tom Simons, money market economist with Jefferies & Co. in New York.

St. Louis Fed President James Bullard, a voting member of the Fed's monetary policy panel this year, said on Friday the Fed could be in a position to halt its asset purchases this year if the U.S. economy improves.

The Fed this week began buying longer-dated Treasuries in an open-ended stimulus program that replaced its "Operation Twist" stimulus, under which it was selling shorter-dated Treasuries and using the proceeds to buy longer-dated U.S. government debt. Twist expired at the end of December, with analysts noting the central bank had few shorter-dated Treasuries left to sell.

The central bank is already buying about $40 billion per month of mortgage-backed securities in an effort to prop up the economy.

The median of forecasts from 13 primary dealers was for the Fed to buy a total of $540 billion of Treasuries under the current stimulus program. Estimates ranged from $270 billion to $1 trillion.

Nine of 16 primary dealers said the U.S. unemployment rate would fall to 6.5 percent in 2015, while six said it would dip to that level in 2014 and one said it would happen in 2016.

The Fed at the conclusion of its December policy meeting said it expects to hold interest rates at the current level of zero to 0.25 percent at least as long as the unemployment rate remains above 6.5 percent and inflation between one and two years ahead is projected to be no more than 2.5 percent.

Previously, the Fed had said it expects to hold rates near zero at least through mid-2015.

The Reuters poll was conducted on Friday after the government reported the pace of hiring by U.S. employers eased slightly in December, while the unemployment rate held steady from November at 7.8 percent.

"In the context of the Fed's now explicit unemployment rate target, (Friday's payrolls data) at the margin theoretically extends the timing of the first tightening," said Tom Porcelli, chief U.S. economist at RBC Capital Markets in New York.

"That said, at the current six month pace in monthly payroll gains and labor force growth, the unemployment rate would still hit 6.5 percent by June 2014 - much sooner than the Fed's prior mid-2015 launch point," he said.

There are 21 U.S. primary dealers. Not all of the dealers responded to the Reuters poll.

(Additional reporting by Pam Niimi; Editing by)