WASHINGTON — A record number of Americans favor withdrawing U.S. forces from Afghanistan as soon as possible, according to a new poll by the Pew Research Center.

The result comes one day ahead of President Barack Obama’s speech on a plan to draw down military forces from Afghanistan. Anti-war liberals, joined by some cost-sensitive Republicans, have recently pushed harder for a more rapid withdrawal as public support of the war has been subsiding since the killing of al-Qaida mastermind Osama bin Laden.

Fifty-six percent of Americans say U.S. troops should be brought home as soon as possible, while 39 percent favor keeping troops in Afghanistan until the situation has stabilized, the survey showed.

This is the first time a majority of Americans support a quick withdrawal. The proportion has increased by eight points since last month, immediately after the killing of bin Laden.

The poll also showed 56 percent of Americans say it is unlikely that Afghanistan will be able to maintain a stable government after the U.S. military leaves.

There are approximately 100,000 U.S. forces in Afghanistan, including a so-called “surge” of 30,000 troops Obama ordered to the country in late 2009. The president planned to begin withdrawing troops in July, with the goal of handing lead security responsibility to Afghan forces by the end of 2014.