A new poll of Afghan voters shows President Hamid Karzai with a big lead just 10 days before the country's presidential election, but not by a margin enough to avoid a run-off.

Karzai has the support of 45 percent of those surveyed. His closest competitor, former Foreign Minister Abdullah Abdullah, has 25 percent.

If no candidate gets more than 50 percent of the vote in the Aug. 20 election, the top two finishers go to a run-off.

The poll by the Washington-based Glevum Associates surveyed 3,556 voting-age Afghans nationwide in mid-July. The poll has a margin of error of 1.6 percent.

The survey is the first to be conducted in the country since campaigning began.