Pakistan summoned the U.S. ambassador Thursday to protest a suspected American missile strike deep inside its territory as militants threatened revenge attacks unless the cross-border raids stop.

The anger came even as NATO forces in Afghanistan said Pakistan's military had responded to a request to attack insurgents on its side of the border, the latest example of what the alliance says is growing cooperation along the frontier.

The United States has staged some 20 missile strikes and at least one commando assault inside Pakistan since August, a barrage seen as a sign of Washington's frustration with the inability of its nuclear-armed ally to curb militants blamed for rising attacks in Afghanistan.

Prime Minister Yousuf Raza Gilani on Thursday denied speculation Islamabad had a secret deal with America allowing the attacks, and said he expected them to stop when U.S. President-elect Barack Obama takes over in January.

"I think these things are happening because of this transition period," he told lawmakers. "I am sure when the government of Sen. Obama is formed, attacks like these will be controlled."

Obama has not directly addressed the issue, but his pre-election comments on the militant threat in Pakistan were hawkish and analysts expect him to carry on with the raids.

Pakistani officials said at least two U.S. missiles destroyed a house in Pakistan's Bannu district on Wednesday, in the first such attack outside the tribal areas directly bordering Afghanistan.

The U.S. rarely confirms or denies involvement in strikes inside Pakistan, which are believed to be carried out mainly by unmanned CIA drones flown across the border.

Bannu adjoins North Waziristan, part of the tribal belt where Pakistan's government has little control and which is considered a possible hiding place for al-Qaida chief Osama bin Laden.

Pakistan's Foreign Ministry summoned the U.S. Ambassador Anne Patterson to protest the strikes for the second time since August. A spokeswoman for the U.S. Embassy said it would convey Pakistan's message to Washington.

Meanwhile, a spokesman for North Waziristan militant leader Hafiz Gul Bahadur warned that his men would launch suicide attacks on foreigners and government targets across the country unless the raids stop.

"The Pakistani government is clearly involved in these attacks by American spy planes so we will target government interests as well as foreigners," Ahmedullah Ahmedi told The Associated Press.

Other militant groups in Pakistan have already launched scores of attacks over the last 18 months, heaping pressure on its secular, pro-Western leaders.

The government complains that the missile attacks fan already widespread anti-American sentiment in Pakistan and undermine its own growing efforts to counter Islamic extremism.

It secured a peace deal with Bahadur's group in February and has been trying to avoid a conflagration in Waziristan at a time when the army is already embroiled in fierce fighting in border regions further north.

However, the country relies heavily on U.S. financial aid and has not gone beyond voicing criticism of American tactics.

Despite the tensions, NATO and U.S. officials say coordination between security forces along both sides of the mountainous frontier between Afghanistan and Pakistan is improving.

A statement from the NATO-led International Security Assistance Force said insurgents hit one of its remote bases and a nearby Afghan border checkpoint with rockets in the eastern province of Paktika on Tuesday.

"After the attacks, ISAF contacted the Pakistani military for support. The Pakistani military then launched a mortar strike on the insurgents' firing location inside Pakistan," it said.

There were no reports of NATO of Pakistani casualties. NATO didn't mention any militant losses. Pakistani military officials were not immediately available for comment.