WASHINGTON (AFP) – The top US military officer is vowing long-term commitment to Afghanistan, touting progress in the war against the Taliban and its Al-Qaeda allies ahead of an American drawdown.

Admiral Mike Mullen, the chairman of the Joint Chiefs of Staff, said on the "Charlie Rose" television interview show Tuesday that although some troops would be withdrawn, a continued US presence was assured.

"Since I've been out there in the last three and a half, four years, it's still the leading question is, 'You left us before, are you going to leave us again?'" he said.

"A couple years ago I got to the point where they're only going to believe we're going to be there if we're there... and certainly there will be some troops that come out this summer... and yet that isn't a message that we're leaving."

President Barack Obama is expected to decide in the coming weeks whether or how many of the 100,000 US troops to withdraw from Afghanistan starting next month, the first stage of a drawdown he initially promised in mid-2009 but later de-emphasized.

Authority is due to be turned to the Afghans in full in 2014.

In 1989, the United States essentially turned its back on Afghanistan after CIA-backed insurgents beat out Soviet forces toward the end of the Cold War. A civil war ensued and the Taliban eventually gained control.

But Mullen insisted America would not repeat its past mistakes.

While hailing the fragile progress made in the 18 months since Obama announced a troop surge to push back the Taliban and buy time for Afghan political and security development, Mullen declined to indicate just how many troops may return home initially.

"We're not picking any numbers yet," Mullen said.

"Whatever that number is from a standpoint of the overall campaign, I'm comfortable we've made enough progress where we can take out a number and continue to make progress in the campaign, and move to 2014 in transition."

He pointed to a "very aggressive agenda to turn the security over by the end of 2014 and to have the governance process and the development process enough in support so that the country can be secure."

The Pentagon, led by outgoing Defense Secretary Robert Gates, seeks only a cautious drawdown from a war that has killed around 1,500 US troops.