ISLAMABAD, Pakistan — Pakistan’s military has ordered its forces to open fire if American troops launch another air or ground raid across the Afghan border, an army spokesman said today.

The orders, which come in response to a highly unusual Sept. 3 ground attack by American commandos, are certain to heighten tension between Washington and a key ally against terrorism.

Pakistan’s civilian leaders have protested the raid but say the dispute should be resolved through diplomatic channels.

However, an army spokesman Major General Athar Abbas told The Associated Press that after American helicopters ferried troops into a militant stronghold at the South Waziristan tribal region, the military told field commanders to prevent any similar raids.

“The orders are clear,” General Abbas said in an interview. “In case it happens again in this form, that there is a very significant detection, which is very definite, no ambiguity, across the border, on ground or in the air: open fire.”

American military commanders accuse Islamabad of doing too little to prevent the Taliban and other militant groups from recruiting, training, and resupplying in Pakistan’s wild tribal belt.

Pakistan acknowledges the presence of al-Qaida fugitives and its difficulties in preventing militants from seeping through the mountainous border into Afghanistan.

However, it insists it is doing what it can and paying a heavy price, pointing to its deployment of more then 100,000 troops in its increasingly restive northwest and a wave of suicide bombings across the country.