WASHINGTON – Defense Secretary Robert Gates said Thursday he has “real concern” about a sharp rise in attacks in eastern Afghanistan, and he blamed the spike on Pakistan's failure to put pressure on insurgents there.

Gates said he welcomed recent vows by Pakistani officials to prevent militants from launching attacks across the border into Afghanistan. And he said he hopes the comments indicate a willingness by Pakistan to assert more pressure on those tribal areas.

“It actually was not bad until a few months ago,” he said, when the Pakistani government began negotiating peace or cease-fire deals with a variety of militant groups in areas bordering Afghanistan.

“The pressure was taken off these people,” as a result of such deals, he added. And that has meant fighters are “now more free to cross the border and create problems for us,” Gates said.

Gates was asked at a Pentagon news conference what he thought of a report by a senior U.S. general in Afghanistan on Tuesday that insurgent attacks in the east have increased by 40 percent this year.

“It is a matter of concern – real concern,” Gates replied. “It's an issue that clearly we have to pursue with the Pakistani government.”

On Wednesday, Pakistan Prime Minister Yousuf Raza Gilani met with his top military and intelligence officials, and later released a statement saying the government would not allow the tribal areas to descend into chaos. Reserving the right to use military force, he said that “Pakistan will not allow its territory to be used against other countries, especially Afghanistan.”

Gates said he believes now that the Pakistanis realize that the militant attacks along the border represent a problem for their own country, as well as Afghanistan.

“The fact that the Pakistani government itself has recognized that this is a problem and that these groups' activities are a problem for the Pakistani government as well as for those of us in Afghanistan, I think is a heartening sign,” said Gates. “I hope we can take advantage of it.”

The U.S. has committed to sending more troops to Afghanistan next year, but any buildup would depend on the Pentagon's ability to reduce troop levels in Iraq.

In other comments, Gates said he has made no decision on whether the Air Force should re-bid the $35 billion refueling tanker contract now that congressional investigators have slammed the process as unfair and riddled with mistakes.

Gates said he is meeting with other Pentagon leaders to determine what to do in the wake of a Government Accountability Office report that found the Air Force failed to evaluate both refueling tanker proposals based on the same merits. It said the Air Force repeatedly offered unfair preference to the team of Northrop Grumman and Airbus parent European Aeronautic Defence and Space Co. over the competing team from Boeing Co.

Still, Gates said he doesn't think it is appropriate for his office to take over the contract and remove it from Air Force control.

“We clearly need to have an approach that has the confidence of the Congress,” Gates said, adding that officials are looking at several options.

Asked if he still has confidence in the Air Force, including Air Force Assistant Secretary Sue C. Payton, Gates offered only a lukewarm assessment.

“We've clearly had problems with the tanker contract,” Gates said. “And this time around is not the first time, obviously. And so, I think I need to get a better feel for the GAO report and for the criticisms and the nature of the criticisms that they have made.”