In this photo released by the Saudi News Agency, King Abdullah bin Abdul Aziz al-Saud of Saudi Arabia, right meets with US Secretary of Defense Robert Gates, third right after his arrival in Riyadh Wednesday, Jan. 17, 2007. [AP]

BAGRAM AIR BASE, Afghanistan - US Defense Secretary Robert Gates suggested Wednesday he would ask President Bush to send more troops to Afghanistan, an increase that could intensify pressure on a US military already straining to wage the war in Iraq.

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After two days of talks with American, NATO and Afghan officials, Gates said he was impressed with progress toward stabilizing and rebuilding Afghanistan. Yet he also said military commanders want to add US troops to the 24,000-strong American force now there, the highest level of a 5-year-old war.

While Gates used no figures, a senior official traveling with him said the prospective increase would not be large - possibly one or two battalions, no more than a couple of thousand soldiers. The official spoke on condition of anonymity because no decision had been made.

Gates stopped short of saying he would recommend the increase. Yet he offered a rationale for reinforcing a war effort that has seen the quick toppling of the Taliban rulers of a country that had been sanctuary for al-Qaida leader Osama bin Laden, only to have combat flare in recent months with renewed Taliban attacks.

"I think it is important that we not let this success here in Afghanistan slip away from us and that we keep the initiative," he told reporters traveling with him. "There's no reason to sit back and let the Taliban regroup."

A US troop increase in Afghanistan would come on top of Bush's decision to send 21,500 more soldiers and Marines to Iraq over the coming four months - adding to the roughly 132,000 already there. That boost had been opposed by many Pentagon uniformed officers, who worry that it would be too much stress on a force that is already sending soldiers to Iraq for multiple tours.

The two wars, each now longer than US involvement in World War II, have stretched American land forces so thin that the Army and Marines are requesting tens of billions more in funding and have persuaded Bush to ask Congress to increase their size.

Gen. Peter Pace, chairman of the Joint Chiefs of Staff, said new troop commitments for Afghanistan would further strain the US military in the short run. But if done as part of a successful strategy against the Taliban, it might hasten the day when the US military can withdraw its combat forces altogether, said Pace, who joined Gates for part of his Mideast trip.

Gates said the number of extra troops "depends on different scenarios," which now will be examined.

Thomas Donnelly, defense specialist with the conservative American Enterprise Institute in Washington, said the military could handle troop increases in both Iraq and Afghanistan, but he added, "It would be an additional straw on the camel's back of American land forces."

Michael DeLong, a retired Marine lieutenant general who was a commander during the wars in Afghanistan and Iraq, said he believed the military could sustain a relatively small troop increase in Afghanistan, but he said the need for the added troops signaled that the conflict was not going as well as hoped.

"When we first went in, the issue in Afghanistan was not to look like the Soviets because too many people become a target," he said, referring to the larger force the Soviet Union sent to Afghanistan a quarter century ago. "Things have changed in Afghanistan, things are not as good as they used to be."

Sen. Hillary Rodham Clinton, D-N.Y., a potential 2008 presidential candidate who just returned from a trip to the Middle East, said commanders in Afghanistan told her they have an urgent need for about 2,300 more troops, including some who might be held in reserve.

"It would be tragic if we fail in Afghanistan because of an unwillingness to deploy a manageable size of additional troops," she wrote in a letter to Gates. The letter was also signed by Sen. Evan Bayh (news, bio, voting record), D-Ind., who was on the trip, too.

Gates said the Joint Chiefs - the top uniformed officers of the Army, Navy, Marine Corps and Air Force - will discuss the increase with Pace, and then Gates will decide what to recommend to Bush. It was not clear how long this might take.

"I think we have the forces" needed to expand the military commitments in both Iraq and Afghanistan, Gates said. "What we have to look at is what the impact is if we were to add more forces here. Ultimately, obviously, it would be the president's decision."

Lt. Gen. Karl Eikenberry, the top US commander in Afghanistan, has already pushed for more troops.

Eikenberry said Tuesday he has asked the Pentagon to order a battalion of the 10th Mountain Division to remain in Afghanistan until the end of the year rather than leave this spring. The unit already is scheduled to deploy to Iraq later this year - an example of how thinly stretched the military has become.

It was not clear how many other troops have been requested for Afghanistan. The US military has about 3,500 troops at Bagram Air Base, which is a hub for air supply operations and is the headquarters of the main US contingent in the country, a brigade of the 10th Mountain Division from Fort Drum, N.Y.

The rest of the US troops are largely in the east, along the Pakistan border, and in the south as part of a NATO-commanded force.

In addition to the US force, NATO has about 20,000 troops around the country.

Gates made a point of saying that NATO, which has yet to deploy about 3,000 of the troops it pledged last year, should fulfill its commitments without delay. He said he would be pressing the allies at a NATO defense ministers meeting - his first since taking office last month - in Spain in early February.

At the midpoint in a weeklong overseas trip, Gates later flew to Riyadh, Saudi Arabia, where he met with King Abdullah and other officials to discuss the situation in Iraq and regional concerns about Iran's nuclear ambitions.

Gates made a pitch for more Saudi help in Iraq, including economic assistance, but made no specific requests, said a senior official speaking on condition of anonymity who attended the talks and briefed reporters later.

The discussion also included Iran, with Gates noting the US decision to send a second aircraft carrier battle group to the Persian Gulf and deploy Patriot missiles in the area. They did not discuss other military plans, the official said.