The chairman of the U.S. Joint Chiefs of Staff, General Martin Dempsey, has arrived in Afghanistan to hold talks with senior commanders.
The visit comes amid a rise of attacks in which apparent Afghan security forces have turned their guns on coalition troops, killing 10 of them in less than two weeks.
The latest such attack occurred in the southern province of Kandahar on August 19, when a man in an Afghan police uniform shot and killed an international service member.
Before landing at the U.S. air base in Bagram, Dempsey said the spike in attacks by members of the Afghan security forces on their NATO counterparts would be a topic of his meetings with U.S.-led coalition and Afghan officers.
Dempsey told AFP news agency and Fox News television that he welcomed President Hamid Karzai's recent statements on the problem, saying he hoped similar comments would be made by lower-ranking officials.
"We speak about it and we're taking measures to mitigate the risk, Dempsey added. But I do think the more they can be as concerned about it as we are, the better off we'll all be."
NATO has some 130,000 troops in Afghanistan who are due to pull out in 2014. The general said the insider violence would not alter the timetable for withdrawal.
On August 18, Defense Secretary Leon Panetta urged Karzai to bolster cooperation with NATO forces to contain the insider threat.
A statement by the Pentagon said measures should include improved intelligence and more rigorous vetting of Afghan recruits.
This year's toll from insider attacks by Afghans on coalition troops reached 40.
Some of the attacks have been claimed by the Taliban who say they have infiltrated Afghan security forces.