Troops have clashed with fighters led by radical Islamist cleric Maulana Fazlullah in the scenic Swat valley of North West Frontier Province for weeks.
More than 300 people have been killed since October, nearly half of them in the last week.
"All the checkposts set up on routes leading to militant [controlled] areas have been ordered not to allow any food items," Major Amjad Iqbal, a military spokesman, said
The food blockade comes as militants continued to put up fierce resistance with rockets and mortars against a fresh military push in the adjoining districts of Swat and Shangla.
On Friday, police foiled a suspected suicide attack in Swat's Kabal town, firing on two militants heading towards a police station after they ignored signals to halt, the military said.
"One individual got killed and the other, believed to be wearing a suicide belt, managed to escape from the scene," the military said in a statement posted on its official website.
Militants also set off a roadside bomb near a security forces convoy elsewhere in the region but caused no damage or casualties, it said.
Violence in Swat, which until recently was a popular tourist resort, surged after Fazlullah called for a jihad, or holy war, to push his campaign to impose a strict Islamic code in the area.
Militants infiltrated from strongholds in the tribal region of North and South Waziristan on the Afghan border to support Fazlullah in recent weeks, as the country's focus has been on Islamabad and President Pervez Musharraf's emergency rule. © 2007 Australian Broadcasting Corporation