The planned withdrawal of more than 30,000 US "surge" troops from Afghanistan will be completed ahead of an end-of-month target date, officials said Friday.

President Barack Obama ordered in reinforcements in December 2009 and last year promised to have the additional troops withdrawn before the end of 2012.

Commanders had aimed to have the troops out by the end of September and defense officials say the drawdown is ahead of schedule.

US troop levels in Afghanistan, which rose to about 100,000 at the peak of the surge, are now down to 77,000, according to a Pentagon tally. When all the surge forces are withdrawn, the American contingent will be down to 68,000 troops.

In January, there were about 90,000 American boots on the ground and by early August, the force had declined to 84,000.

There are about 40,000 non-US troops deployed in the NATO-led coalition.

NATO countries plan to pull out the bulk of their combat forces by the end of 2014 after a gradual handover to Afghan army and police.

But the commander of US and NATO troops in Afghanistan, General John Allen, has yet to issue a recommendation to the White House on troop levels for next year.

In an interview with Foreign Policy magazine this week, Allen said he would provide his advice in November -- after the US presidential election.

"My goal now is to have something out of here by the middle of November," he was quoted as saying.

The general made no mention of the November 6 election but any decision on the pace of the troop drawdown in Afghanistan would become fodder for the hotly contested campaign.