Should the president decide to send a smaller number than that, 56 percent would oppose that decision and 42 percent support it with 2 percent undecided, according to the poll, which was conducted Nov. 13-15.

Obama reportedly has been weighing four options, ranging from sending a low of 10,000 more troops to as high as the 40,000 requested in September by Gen. Stanley McChrystal, the top U.S. commander in Afghanistan.

The poll found that 52 percent of Americans now oppose the war, compared to 45 percent who support it with 3 percent undecided. The percentage of those opposed is lower than in the previous four months, when opposition was either at 57 percent or 58 percent.

"The war is unpopular and previous polls have shown that Americans oppose sending more troops in the abstract," said CNN Polling Director Keating Holland. "But it may be a different story when Americans are confronted with an actual decision, by the commander-in-chief, on a military matter. Previous presidents have seen a 'rally effect' -- at least temporarily -- when they have made command decisions like this one."

Sixty-six percent believe the war is going moderately to very badly, while 32 percent said it was going moderately to very well (only 2 percent said "very well").