WASHINGTON — Military commanders did not recommend that the White House announce the complete withdrawal of U.S. troops from Afghanistan in 2017 as the president ordered, the top U.S. commander there told senators Thursday.Marine Gen. Joseph Dunford said U.S. and Afghan military leaders would have preferred to see American officials be "a bit more ambiguous" about the troop numbers for 2017 and not telegraph to the enemy that international forces would leave.Speaking before the Senate Armed Services Committee, Dunford laid out a sober assessment of the Afghan security forces, saying there will still be critical aviation and intelligence-gathering gaps in their ability to conduct counterterrorism operations in 2016.He said the Afghan special forces would not be capable on their own by 2017 of applying adequate pressure on al-0aida. And he said that if Afghanistan and Pakistan don't keep pressure on extremists in both countries, there is a "significant" risk that al-Qaida could repopulate Afghanistan and resume effort to plot attacks against the United States.Asked about the potential for changes to the U.S. withdrawal plans, Dunford said under the current schedule U.S. forces would shift from other locations around the country to the Kabul area in 2016, significantly reducing U.S. ability to assist in the counterterror fight.He said if the U.S. decides more help is needed in 2016, officials will have to start discussing that a year from now in order to have American special operations forces available beyond Kabul to assist in that fight.Dunford has been nominated to be the next commandant of the Marine Corps and was testifying at his nomination hearing.President Barack Obama ordered the U.S. to withdraw all but nearly 10,000 troops by the end of 2014, cut that number in half by the end of 2015 and leave only about 1,000 in a security office after the end of 2016. In addition to the U.S. forces, other NATO nations would contribute 4,000 troops, Dunford said, adding that the totals include about 2,000 U.S. special operations forces. Of those, he said about 1,000 would be dedicated solely to counterterror operations.Dunford told the panel that he agrees with the pace of the U.S. withdrawal this year and next year. But, under questioning from Sen. John McCain, R-Ariz., he said he and other military leaders did not recommend "a hard date" for the full withdrawal at the end of 2016. He said military leaders prefer to routinely re-evaluate troop decisions based on conditions on the ground, including the capability of the Afghans, the state of the threat from militants and the progress of the Afghan government."Every military leader would want to have the conditions on the ground and the assumptions be revalidated as a transition takes place," Dunford said.Other senators expressed similar worries."I remain very troubled by the president's plan to draw down our forces based on arbitrary timelines instead of the advice of our commanders, and the facts on the ground," said Sen. James Inhofe, R-Okla. "The president tried the same policy in Iraq in 2011. We can't afford to repeat that same mistake in Afghanistan."Dunford said a key element for success in Afghanistan is Pakistan's ability and desire to go after militants on that side of the border. While he said Pakistan is having some success against the Pakistani Taliban, they have had less of an effect against the Haqqani network, which has strong links to the Taliban and conducts attacks against U.S. forces across the border in Afghanistan.Asked how well the Afghans and Pakistanis are cooperating, Dunford said he would grade them a "D."Dunford also offered a strong endorsement for continuing to provide Russian MI-17 helicopters to the Afghan forces, saying that prohibiting their sales would be "catastrophic."U.S. lawmakers have urged stronger penalties against Moscow due to the incursion into Ukraine's Crimean Peninsula, and they have called for the termination of the remainder of a $1 billion contract to buy the Russian helicopters.Dunford said about 30 of the helicopters are for the Afghanistan's special operations forces, and without the aircraft, the Afghans would not be able to do their counterterror operations as well. He added that losing those helicopters would also degrade the Afghans' abilities to protect U.S. forces, increasing the danger to Americans there.