The U.S. military chief met with Pakistani officials Wednesday a day after Pakistan's army said its forces have orders to fire on U.S. troops if they cross the Afghan border again to launch attacks on militants inside Pakistan.

Adm. Mike Mullen, chairman of the joint chiefs of staff, arrived in Pakistan late Tuesday to discuss a range of issues, including ways to improve coordination and cooperation, in the wake of Pakistani anger over a Sept. 3 ground attack by U.S. commandos in a border area.

He met separately with army chief Gen. Ashfaq Parvez Kayani and Prime Minister Yousuf Raza Gilani but made no comment to waiting reporters. It was not clear how long Mullen would be in Pakistan.

Mullen arrived the same day that Pakistan's army said its forces have orders to open fire if U.S. troops launch another raid across the Afghan border, raising the stakes in a dispute over how to tackle militant havens in Pakistan's unruly border zone.

Pakistan's government has faced rising popular anger over the Sept. 3 attack by U.S. commandos into South Waziristan, a base for Taliban militants who have been killing increasing numbers of U.S. troops in Afghanistan. Pakistan says about 15 people were killed in the raid, all civilians.

The new firing orders were disclosed by Pakistani army spokesman Maj. Gen. Athar Abbas in an interview Tuesday with The Associated Press.

Abbas said Pakistani field commanders have previously been tolerant about international forces crossing a short way into Pakistan because of the ill-defined and contested nature of the mountainous frontier.

"But after the (Sept. 3) incident, the orders are clear," Abbas said. "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."

The statement was the strongest since Kayani raised eyebrows last week by vowing to defend Pakistani territory "at all cost." Abbas would not say whether the orders were discussed in advance with U.S. officials.

The Democratic chairman of the U.S. House of Representatives Foreign Affairs Subcommittee on South Asia, Gary Ackerman, and other U.S. lawmakers expressed concern about Abbas' comments at a hearing Tuesday to examine a White House request to fund an upgrade of Pakistan's aging fleet of F-16 fighter planes.

Responding to the concerns, Donald Camp, deputy assistant secretary of state for South Asian affairs, said: "I cannot envision a situation where we would find ourselves in a shooting situation with Pakistan."

U.S. military commanders complain Islamabad has been doing too little to prevent the Taliban and other militant groups from recruiting, training and resupplying in Pakistan's lawless tribal belt.

Pakistan acknowledges the presence of Al Qaeda fugitives and its difficulties in preventing militants from seeping 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 the increasingly restive northwest and a wave of suicide bombings across the country.

Pakistani troops backed by jet fighters continued targeting militant positions Wednesday outside Khar, the main town in the Bajur tribal area, killing at least 10 insurgents and wounding 13 others, said Iqbal Khattak, a government official in Bajur.

Also Wednesday, police said a homemade bomb went off outside a home late Tuesday in the northwestern city of Dera Ismail Khan, damaging several houses and killing a woman and wounding seven others. No one claimed responsibility.