WASHINGTON – The Obama administration is holding off major decisions that could put its military forces on a firmer war footing in Afghanistan even as doubts grow about whether the United States can win there.

Many military and diplomatic leaders have urged President Barack Obama to send thousands more Marines, soldiers and pilots to try to reverse Afghanistan’s crumbling security situation.

But White House spokesman Robert Gibbs has said no decision about adding troops is expected for ‘weeks and weeks,’ following what he described as intensive evaluation. The troop decision will be a first indicator of whether Obama intends to double down in Afghanistan, becoming a wartime president in earnest.

Leading Democrats in Congress have signaled they do not support a troop increase now, and maybe not at all. The chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, had the unhappy task of telling the Senate Armed Services Committee yesterday why the United States should stay the course and commit additional forces.

Mullen gave no figure, but said doing the job right will take more people.

‘We can get there. We can accomplish the mission we’ve been assigned, but we will need more resources,’ Mullen said during his nomination hearing for a second term as the president’s chief military adviser.

Sitting directly in front of him was the panel’s influential chairman, Sen. Carl Levin, D-Mich., who warned the White House last week not to push for a big troop increase. He wants the Pentagon to focus instead on quicker training for Afghan security forces.

Mullen has sounded increasingly alarmed about the growing technical capabilities of a resurgent Taliban and about the lackluster support among Afghans for the foreign-run enterprise that purports to protect them from a homegrown insurgent movement.

‘Time is not on our side,’ Mullen said earlier this month.

But Obama said this week that he is in no hurry to change the dynamic in Afghanistan.

‘Over the next several months, what people need to do is to not expect a sudden announcement of some huge change in strategy,’ Obama told CNBC on Monday. He reiterated the main goal – targeting the al-Qaida terror network – but also mused about the perils of fighting a war without full backing at home.

‘Afghanistan is not Vietnam, but the dangers of overreach and not having clear goals and not having strong support from the American people, those are all issues that I think about all the time,’ Obama said.

Postponing whether to add more American forces and alter other aspects of military strategy could give the White House breathing room for other priorities, including a health care overhaul and a hard-fought defense budget package.

Leading congressional Republicans, who have become Obama’s strongest supporters for the Afghan effort, are fretting that he will punt.

Sens. John McCain, R-Ariz., Lindsey Graham, R-S.C., and Joseph Lieberman, I-Conn., warned in a Wall Street Journal essay on Monday that muddling through is a recipe for disaster.

‘More troops will not guarantee success in Afghanistan, but a failure to send them is a guarantee of failure,’ they wrote.

Fifty-one U.S. troops died in Afghanistan in August, more than any other month since the U.S.-led invasion in October 2001. The rising casualty toll and the addition of 21,000 U.S. forces this year have heightened public scrutiny of what was once called the ‘forgotten war.’ Now Iraq holds that distinction, although nearly twice as many U.S. soldiers remain stationed there than in Afghanistan.

Recent national polls indicate slipping support for the nearly eight-year war and growing doubt that it can be won. The latest AP-GfK survey finds that fewer than half – 46 percent – now approve of Obama’s handling of Afghanistan, a 9 percentage point drop since July.

A CNN poll conducted this month said 39 percent supported the war and 58 percent opposed it. That compared with 53 percent supporting and 46 percent opposing in early April, days after Obama announced a new war strategy and vowed to provide resources to the war effort in ways his predecessor had not.

‘I just don’t know that more troops is the answer,’ Sen. Susan Collins, R-Maine, said Sunday on CNN. She is also a member of the Senate Armed Services Committee. ‘I’m just wondering where this ends and how we’ll know if this succeeded.’

Gen. Stanley McChrystal, the top U.S. commander in Afghanistan, is widely expected to ask for more forces for what he describes as a nearly complete do-over of the Bush administration’s strategy to fight an increasingly unpopular war.

That request is expected within two weeks, following a summer-long review and a classified assessment of the prospects for applying the revamped counterinsurgency strategy that Obama outlined earlier this year.

Congressional defense leaders are due to be briefed this week on McChrystal’s assessment, which was the subject of a White House huddle with top military leaders Sunday. The White House is also due to submit a set of Afghanistan benchmarks or performance tests to Congress next week.

The White House has been vague about what happens next, but Gibbs’ rough timeline suggests that any choices about whether to escalate the war will come after the worst of the fighting for this year. Because of the cold, fighting tends to ebb in mid- to late fall and begin again in earnest in mid-spring.

‘I think it will be many weeks of evaluation and assessment,’ Gibbs said.

Editor’s note: Anne Gearan covers national security policy for The Associated Press.