A U.S. soldier of the 101st Airborne Division is seen during a patrol, as Afghan boys look on in Khost, Afghanistan. U.S. troop levels in Afghanistan now top 32,000, the highest number of American forces in the country since the 2001 U.S.-led invasion that toppled the Taliban. U.S. military officials would like to see the NATO-led force grow by several thousand more troops, but American resources are stretched too thin and no other country is stepping up.

Washington ? While America’s attention remains focused on Iraq, violence is escalating in Afghanistan, worrying senior U.S. defense officials and commanders struggling to find some 7,000 more American and European troops to combat resurgent Taliban and al-Qaida forces.

There are indications that Islamic militants may have adopted a new strategy of avoiding U.S and NATO forces and staging attacks in provinces that haven’t seen major unrest and on easy targets such as aid organizations and poorly trained Afghan police.

A roadside bomb reportedly killed two policemen and injured three Tuesday in southern Afghanistan, a day after insurgents killed 11 police officers.

A majority of America’s NATO allies continue to balk at U.S. requests to send thousands more of their troops to Afghanistan. At the same time, the renewed violence in Iraq and the White House decision to suspend further American troop withdrawals from Iraq this summer will make it harder for the Pentagon to send more American forces to Afghanistan next year as President Bush has promised.

“I’m deeply concerned,” Adm. Michael Mullen, the chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee last Thursday. “In this economy of force operation, we do what we can. Requirements exist that we simply cannot fill and won’t likely be able to fill until conditions improve in Iraq.”

Some 3,500 additional U.S. Marines arrived in southern Afghanistan recently, but they’re due to leave at the end of the year and no replacements have been identified.

Last year saw the worst bloodshed in Afghanistan since the 2001 U.S.-led intervention that overthrew the Taliban regime and drove Osama bin Laden and his core supporters into Pakistan’s remote tribal region, where they’ve re-established bases for training terrorists and plotting new attacks, according to U.S. intelligence officials.

With Afghanistan due to hold a presidential election next year, pressure is growing on the United States and NATO to contain the insurgency so the U.S.-backed government of Prime Minister Hamid Karzai and the United Nations can proceed with the complex preparations.

Several new reports by nongovernmental groups have found that insurgent violence has surged in the first months of this year to a level as high as or higher than it was during the same period last year.

“The data demonstrates a solid escalation of conflict within the first three months of the year as well as a substantial growth over the same period last year,” says a study by the Afghanistan NGO Safety Office, a group funded by the European Commission that charts security trends for nongovernmental organizations, such as aid organizations.