(Chip Somodevilla/GETTY IMAGES)

Allen, whom Obama has nominated to become commander of U.S. and NATO forces in Afghanistan, said he wasn’t involved in the deliberations over how many troops to pull out from Afghanistan. But he echoed other military commanders in saying that Obama’s decision to withdraw 10,000 troops by December and 23,000 more troops by September “was a bit more aggressive than we anticipated.”

At the same time, Allen said Obama’s timetable to wind down the war in Afghanistan sent a clear message to the government of President Hamid Karzai that it needs to assert itself and take more direct responsibility for fighting the Taliban.

“It sends a message of urgency to the Afghans that they must begin to take ownership of their security themselves,” Allen said.

Allen’s testimony came as the Senate panel considered a triple play of military nominations. In addition to Allen’s promotion to full general and the top commander in Afghanistan, the committee deliberated on the nomination of Vice Adm. William H. McRaven to become commander of the U.S. Special Operations Command and Army Gen. James D. Thurman to become commander of U.S. forces in Korea.

Confirmation appeared to be a foregone conclusion in each case as effusive senators praised the patriotism and bravery of the nominees. The toughest questions for McRaven, the current head of the Joint Special Operations Command and the military official who oversaw the raid that killed Osama bin Laden, concerned whether he thought he’d have enough forces and support to keep pursuing insurgent leaders in Afghanistan.

Allen had the more awkward task of persuading senators that he backed Obama’s troop drawdown plan even though it was an open secret that the Pentagon wanted the commander in chief to keep more forces in Afghanistan for a longer duration. “This decision by the president can be accounted for in the current strategy,” Allen said, a bit delicately.

The former deputy commander of the U.S. Central Command, Allen also fielded skeptical questions about whether the U.S. strategy in Afghanistan could succeed regardless of how many U.S. forces stick around.

“I have for you a more fundamental question,” said Sen. Susan Collins (R-Maine). “Is there any number of troops that can ensure a stable Afghanistan?” She cited the existence of havens for insurgents in Pakistan and the lack of a functional government in Kabul “that is not plagued by corruption.”

Allen acknowledged that “there are challenges, significant challenges” but said those obstacles were not insurmountable.

McRaven was more forthright about the U.S. government’s inability to persuade Pakistan to eliminate havens for insurgents fighting in Afghanistan. Asked why Pakistan hadn’t cracked down on the Haqqani network, which is based in North Waziristan, McRaven said it was “both a capacity issue and potentially a willingness issue,” and added, “I don’t think it is likely to change” in the near term.

That assessment didn’t improve the mood of some senators, already irritated by what they view as a lack of support from Pakistan. “Something’s got to give, something’s got to change,” said Sen. Carl Levin (D-Mich.), the committee chairman.

Sen. Lindsey Graham (R-.S.C.) pressed the point on whether Pakistan was a reliable partner by asking McRaven if Pakistan had acted on U.S. requests to find Mullah Omar, the Taliban’s spiritual leader, or to close down bomb factories operating on its territory.

McRaven acknowledged that U.S. officials had asked their Pakistani counterparts for help on both counts, but didn’t have much to show for it. “I’m with Chairman Levin on this,” Graham said, citing a growing frustration with Pakistan. “This has got to stop.”

Levin said the committee would try to hold a confirmation vote for Allen and the others this week. Administration officials want to speed up plans to change commanders in Afghanistan so that Gen. David H. Petraeus, the current commander, has a bit of a breather before starting his new job, as expected, as director of the CIA.