U.S. military leaders said Thursday that President Obama’s decision to remove forces from Afghanistan in the middle of a fighting season poses some risk to recent battlefield gains but publicly supported his plan to bring home 33,000 troops by the end of next summer.

Neither his civilian advisers nor his military commanders won all that they had sought in Obama’s withdrawal decision, which will bring home 10,000 troops this year and another 23,000 by September 2012. But Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, and Gen. David H. Petraeus, the commander in Afghanistan, said in testimony on Capitol Hill that they believed the president had heard their proposals and set a policy they can carry out.

“The ultimate decision was a more aggressive formulation, if you will, in terms of the timeline, than what we had recommended,” Petraeus told the Senate Intelligence Committee during a hearing on his nomination to head the CIA. “That is understandable in the sense that there are broader considerations beyond just those of a military commander.”

In the weeks leading up to his decision, Obama faced growing calls from Congress to swiftly draw down U.S. forces and narrow the mission to focus on destroying al-Qaeda, abandoning some of the expensive nation-building tasks that are part of the counterinsurgency strategy championed by Petraeus.

Lawmakers have offered a mixed reaction to Obama’s decision. Some have criticized the drawdown as too precipitous a withdrawal given the fragility of recent successes, while others have said it is too slow given the mounting domestic demands that are being neglected as a result of the $10 billion-a-month war effort.

But Mullen and Petraeus said that Obama effectively assessed the ramifications of withdrawing forces at the pace he chose and that the military would be able to carry out its mission effectively. The drawdown will leave 68,000 U.S. troops in Afghanistan by the end of next summer, still a larger force than when Obama took office.

“The fact is that there’s never been a military commander in history who has had all the forces that he would like to have, for all the time, with all the money, all the authorities, and nowadays with all the bandwidth as well,” Petraeus said.

His comments echoed Mullen’s testimony earlier in the day before the House Armed Services Committee. Together the military leaders managed to blunt criticism, especially from some Republican lawmakers, that Obama’s decision was driven more by political considerations than strategic ones.

At the end of 2009, Obama ordered an additional 33,000 troop to Afghanistan after a months-long strategy review designed to change the downward trajectory of the war. His schedule to bring those troops home will conclude two months before voters decide whether to elect him to a second term. After nearly a decade, a majority of the country no longer believes the war in Afghanistan is worth fighting.

Petraeus, who helped design the 2009 troop surge, told the Senate committee Thursday that “there is always a process of assessing risk, and it’s typically, in a case like this, as the chairman [Mullen] put it today, risk at the margin.”

“We’re talking about small differences here, albeit significant from a military commander point of view,” he said.

Military leaders had sought to keep the vast majority of the surge forces in Afghanistan through the end of 2012, giving them another full fighting season in addition to the one underway.

In agreeing to the escalation in 2009, Obama set July 2011 as the date he would begin bringing those troops home. Commanders, in the words of one administration official who like others spoke on condition of anonymity to discuss internal deliberations, wanted only a “small down payment” of troops withdrawn this year to meet that deadline.

Obama’s civilian advisers argued for a faster drawdown, citing military gains against al-Qaeda that have exceeded expectations, including the May killing of Osama bin Laden and progress in training Afghan security forces.

Addressing troops of the 10th Mountain Division on Thursday during a visit to Fort Drum in upstate New York, Obama cited those achievements, saying that “we have turned a corner where we can begin to bring back some of our troops.”

“We’re not doing it precipitously,” he said. “We’re going to do it in a steady way to make sure that the gains that all of you helped to bring about are going to be sustained.”

Administration officials said the most aggressive withdrawal option presented to Obama called for 15,000 troops to be removed this year and another 18,000 by the end of next spring. The plan Obama adopted came down between the civilians’ spring timeline and the military’s end-of-year one.

“There is no jumping ship here. Quite the contrary,” Mullen told the House committee. “We will have at our disposal the great bulk of the surge forces throughout this and most of the next fighting season.”

In arguing to keep the surge forces in Afghanistan, military commanders outlined a plan to redeploy the troops from the south, where they have been fighting over the past 18 months, to several eastern provinces. Obama, one administration official said, ordered them home instead.

“If our task were to defeat every last remnant of the Taliban, then we would have,” the official said. “But it isn’t.”

Senior U.S. military officials had worried about a drawdown so steep that they would be forced to abandon the counterinsurgency approach — a mix of combat and stabilization operations — underway in southern Afghanistan and parts of the east.

“This will require tweaking the campaign plan, but it does not force us to abandon counterinsurgency for counterterrorism,” said one senior military official who spoke on condition of anonymity to describe internal planning.

One near-term change will be to accelerate the training of Afghan security forces, military officials said. In some cases, they said, Afghan forces may have to operate without the support of U.S. battalions to clear lower-priority areas in eastern and northern Afghanistan.

“So much depends on the Afghan forces stepping up, which they can do, and a more skillful wielding of carrots and sticks with the Afghan [military] leadership,” the senior military official said.

Staff writer Greg Jaffe contributed to this report.