Public support for the war in Afghanistan grew by nine percentage points to 57 percent in the past three weeks, says a poll released Tuesday.

The Quinnipiac University poll also found that Americans' approval of President Barack Obama's handling of the war was up seven points in the same period, from a 38-49 percent negative on Nov. 18 to a 45-45 percent split.

Americans also approved 60-32 percent of the president's plan to begin withdrawing combat troops from Afghanistan in July 2011.

By a 45-40 percent margin, however, more Americans do not believe Obama will be able to keep that promise than those who do.

The poll shows that Obama's nationally televised Dec. 1 speech on Afghan strategy has worked, at least in the short term, said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

The survey was conducted Dec. 1 to Dec. 6 among 2,313 registered voters nationwide.

Obama delivered a prime-time speech to the nation on Dec. 1, laying out a strategy that calls for sending 30,000 more troops to Afghanistan and starting a withdrawal of U.S. forces in July 2011.