Americans are divided on whether the war in Afghanistan has been worth fighting and the requests by top military commanders to send more troops, according to a Washington Post/ABC News poll conducted Oct. 15-18.

By margins of 49 percent to 47 percent, those polled do not think the war was worth fighting and oppose sending more forces to the country. The margin of error is 3 points.

They also split on President Obama's handling of the situation in Afghanistan, with 47 percent disapproving and 45 percent approving. That's a sharp falloff from September, when 55 percent approved and 37 percent disapproved.

As Obama and his advisers mull the request made last month by Gen. Stanley McChrystal, the top U.S. commander in Afghanistan, for as many as 40,000 more troops, 31 percent of respondents say that the administration does not have a clear plan for handling the situation there. Sixty-three percent had no opinion.

Despite those divisions, 79 percent say the U.S. should try to keep the Taliban out of power, even if it determines that the group did not support terrorism against the U.S.

The goals those polled most support (at 75 percent each) are preventing establishment of al-Qaida bases and the return of the Taliban. Sixty-eight percent support attacks on leaders of al-Qaida, the Taliban and similar groups across the border in Pakistan. There is less support (59 percent) for economic aid to improve living conditions for ordinary Afghans and getting the U.S. involved in establishing a stable Democratic government.

Two-thirds believe the recent election in Afghanistan was fraudulent.

Fifty-eight percent believe the U.S. will avoid getting involved in a Vietnam-like quagmire while 35 percent fear it will. That's an opposite result from a CNN poll conducted Oct. 16-18, which had 52 percent believing the U.S. was headed down the same route as in Vietnam and 46 percent disagreeing.