WASHINGTON — Strong support has coalesced in the Pentagon behind a military plan to "double down" in Iraq with many more U.S. troops, an increase in industrial aid and a major combat offensive against Muqtada al-Sadr, the Shiite leader undermining Iraq's government.

The Joint Chiefs of Staff will present their recommendations to President Bush today. Military officials, including some advising the chiefs, have argued that an intensified effort might be the only way to get the U.S. counterinsurgency strategy right and provide a chance for victory.

Meanwhile, the Army and Marine Corps plan to seek permanent increases in personnel because top officials in both services say that the nation's global military strategy has outstripped their resources.

The Army also will press hard for "full access" to the 346,000-strong Army National Guard and the 196,000-strong Army Reserve. That means easing Pentagon restrictions on the frequency and duration of involuntary call-ups for reservists, according to two senior Army officials.

"The Army has configured itself to sustain the effort in Iraq and, to a lesser degree, in Afghanistan. Beyond that, you've got some problems," said one of the senior Army officials. "Right now, the strategy exceeds the capability of the Army and Marines."

The Army, which has 507,000 active-duty soldiers, wants Congress to permanently fund an "end strength," or manpower, of at least 512,000 soldiers, the Army officials said. The Army wants the extra troops to be paid for not through wartime supplemental spending bills but in the defense budget, which now covers only 482,000 soldiers.

The Marine Corps, with 180,000 active-duty Marines, seeks to grow by several thousand, including the likely addition of three new infantry battalions. "We need to be bigger. The question is how big do we need to be and how do we get there," a senior Marine Corps official said.

'THIS IS A DOUBLE DOWN'

Sending more troops to Iraq resembles a course promoted publicly by Sen. John McCain, R-Ariz. But the Pentagon proposals add several additional features, including the confrontation with al-Sadr, a possible renewed offensive in the Sunni stronghold of Anbar province, a large Iraqi jobs program and a proposal for a long-term increase in the size of the military.

Such an option would appear to satisfy Bush's demand for a strategy focused on victory rather than disengagement from Iraq. It would disregard key recommendations and warnings of the Iraq Study Group, however, and provide little comfort for Americans fearful of a long, open-ended commitment in Iraq.

"I think it is worth trying," said a defense official, using the gamblers' term for upping a bet. "But you can't have the rhetoric without the resources. This is a double down."

NO GUARANTEES

Such a proposal, military officials and experts caution, still would be a gamble. Any chance of success likely would require major changes in the Iraqi government, they said. U.S. Embassy officials would have to help usher into power a new coalition in Baghdad that was willing to confront the militias. And the new military strategy also would require more spending by the United States, both for growth of the U.S. military and additional money for an Iraqi jobs programs.

"You are dealing with an inherently difficult undertaking," said Stephen Biddle, a military analyst called to the White House this week to advise Bush. "That doesn't mean we should withdraw. But no one should go into this thinking if we double the size of the military the result will be victory. Maybe, but maybe not. You are buying the opportunity to enter a lottery."

The wild card in the Pentagon planning process is Robert M. Gates, due to be sworn in Monday as defense secretary. Gates had breakfast with Bush yesterday morning and will participate, along with Defense Secretary Donald H. Rumsfeld, in today's meetings.

Bush is making a public drive this week to collect recommendations from his administration as he crafts his new strategy for Iraq. But some defense officials say Gates might make a bid for more time so he can weigh other military options. And before endorsing an increase in the number of combat forces, Gates might press commanders in Iraq for assurances that U.S. forces can hold off an escalation of the sectarian civil war that has gripped the country.

"This is the big moment," said the defense official. "It is enormously important for the new secretary of defense to revisit what the overall objective is ... and what is needed to achieve that."

Defense officials interviewed for this article requested anonymity because the deliberations over the Pentagon's recommendations are continuing and have not been made public.

TEST OF WILLS?

Some military officers believe that Iraq has become a test of wills, and the United States needs to demonstrate to insurgents and sectarian militias that it is willing to stay and fight.

"I've come to the realization we need to go in in a big way," said an Army officer. "You have to have an increase in troops. ... We have to convince the enemy we are serious and we are coming in harder."

The exact size of the troop increase the Pentagon will recommend is unclear. One officer suggested an increase of some 40,000 forces would be required, but other officials said such a number is unrealistic.

The problem with any sort of surge is that it would require an eventual drop in 2008, unless the president was willing to take the politically unpopular move of remobilizing the National Guard and sending reserve combat units back to Iraq.

DIFFERING OPINIONS

An increase in U.S. forces is not universally popular in the military. Army Gen. John P. Abizaid, the top American commander in the Middle East, has long argued that increasing the size of the force would be counterproductive, angering the people the U.S. is trying to help.

Outside the Pentagon, other government officials are skeptical that an increase in military power will end sectarian violence. James Dobbins, a former U.S. diplomat and adviser to the Iraq Study Group, said many Iraqis believe that U.S. forces put them in danger, rather than improve security.

"The American troop presence is wildly unpopular in Iraq," Dobbins said. "Any effort to double our bet will lead to ever more catastrophic results."

Some officers argue that the U.S. needs to show substantial progress in decreasing the violence and instability in Iraq before the 2008 presidential election. But other officers and analysts note that a comprehensive counterinsurgency plan will take years, not months, to work.

"You do not want to withdraw your troops until you achieve your mission," said Andrew Krepinevich, a counterinsurgency expert and director of the Center for Strategic and Budgetary Assessments. "We are going to be in Iraq for a long, long time. It is going to be decades before Iraq can be left to its own devices without descending into a civil war."

TROUBLE ELSEWHERE

If a new conflict required a significant number of ground troops — as in some scenarios for Korea, Taiwan or the disintegration of Pakistan — Army and Marine Corps officials made clear that they would have to scramble to provide them. "Is it the way we'd want to do it? No. Would it be ugly as hell? Yes," said one of the senior Army officials. "But," he added, "we could get it done."

According to Abizaid, the Army and Marine Corps today cannot sustain even a modest increase of 20,000 troops in Iraq. U.S. commanders for Afghanistan have asked for more troops but have not received them, noted the Iraq Study Group report, which called it "critical" for the United States to provide more military support for Afghanistan.

Julian E. Barnes of The Los Angeles Times and Ann Scott Tyson of The Washington Post contributed to this report.