The top Marine officer leading the U.S.-led offensive in southern Afghanistan says he needs additional Afghan soldiers to help defeat the Taliban.

Marines Brig. General Larry Nicholson told Pentagon reporters Wednesday that he'd like more U.S. troops as well, but that they're not necessary in the campaign to rout Taliban militants from the country's poppy-growing region.

Nicholson said the greatest danger to the 4,000 U.S. troops leading the operation that began a week ago in Helmand province is unrelenting heat he described "as hot as fire."

Nicholson's Marine unit leaves Afghanistan in the next six to eight months. A unit is scheduled to replace them but unlike the Army, Marine tours are shorter than the 12 to 15 months that soldiers can spend deployed.

There are about 650 Afghan army soldiers and police involved in the operation in Helmand. Nicholson also said it's not clear where the Taliban who have been pushed out have gone.

"The number one question we get from the people is, 'when are you leaving?'" said Brig. Gen. Larry Nicholson, commanding general of Marine Expeditionary Brigade-Afghanistan.

"The answer is we're not leaving until the transition for security is made to the provincial government, to include the Afghan forces."

"I'm not going to sugarcoat it. The fact of the matter is, we don't have enough Afghan forces," Nicholson said during a telephone briefing from Camp Leatherneck in southern Afghanistan. "And I'd like more."

While there is a plan to send more Afghan troops to the region, Nicholson said, "they're just not available right now."

Nicholson said he would like to have all of his Marine battalions paired up with Afghan battalions — a process he predicted would take at least several months.

The Pentagon has long known that training Afghan soldiers would be a large part of the renewed U.S. push in the nation. Earlier this year, Defense Secretary Robert Gates ordered 21,000 additional U.S. troops to Afghanistan — including 4,000 training forces — by the end of September.

Nicholson also said he'd like more U.S. troops in the region, but that "I don't necessarily need more troops."

Joint Chiefs Chairman Adm. Mike Mullen on Wednesday avoided discussing the possibility of sending more troops, telling a National Press Club audience that the new U.S. and NATO commander in Afghanistan, Gen. Stanley McChrystal, was still assessing his force needs.

There were an estimated 57,000 U.S. troops in Afghanistan as of Wednesday. That number is expected to rise to at least 68,000 by the end of 2009.

A Defense official said later Tuesday that the lack of trained Afghan soldiers has not hurt the Helmand operation, but that the mission would run faster and more smoothly with them. The official spoke on condition of anonymity to discuss the operation candidly.

Fighting is continuing in the province, and Nicholson estimated there had been about 20 clashes with the Taliban so far in the weeklong offensive. No civilians have been killed so far, he said.

Nicholson said he did not know where the extremists have fled, although Marines in Helmand say the Taliban relocated to the Marjaa area west of the province.

But he predicted they'll be back to make more money off Helmand's poppy crops.

"The enemy is not just going to stay away," Nicholson said.

The Associated Press contributed to this report.