The Pakistani Taliban are planning to attack foreigners assisting in the aftermath of devastating floods in the country, a senior U.S. official warned.

"According to information available to the U.S. government, Tehrik-e-Taliban plans to conduct attacks against foreigners participating in the ongoing flood relief operations in Pakistan," the official told the BBC on condition of anonymity.

The Taliban "also may be making plans to attack federal and provincial ministers in Islamabad," the British broadcaster quoted the official as saying.

Pakistani Taliban spokesman Azam Tariq hinted at an attack himself, claiming Thursday that the United States and other countries were not really focused on providing aid to flood victims but had other "intentions" he did not specify.

Tariq strongly hinted that the militants could resort to violence.

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"When we say something is unacceptable to us one can draw his own conclusion," he said.

It is not yet clear what effect the terror warning will have on U.S. involvement in the relief efforts, but Pakistan has assured the U.S. it will press its campaign against insurgents inside its borders despite the extraordinary demands on the country's military from the floods, officials said.

The Tehrik-e-Taliban faction is a key architect of extremist violence that has left more than 3,500 dead in Pakistan over the last three years, according to AFP.

U.S. officials had previously said they had not encountered any hostilities in flying aid to stricken parts of the country.

The U.S. military official leading the American flood relief mission in Pakistan said he was confident that Islamabad would continue the fight but deflected questions about whether the pace or scope of its efforts might change.

Pakistan will maintain a "dedicated, committed struggle against violent extremism," Brig. Gen. Michael Nagata said.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said he worries the insurgents will take advantage of the flooding. Insurgent groups could benefit by providing aid that the central government cannot, or by launching attacks or widening their reach during a period when the Army is occupied elsewhere.

At least one of the Muslim charities involved in aid work is alleged to be a front for Lashkar-e-Taiba, a banned militant organization blamed for the 2008 attacks in Mumbai, India.

"There are millions who are affected right now in Pakistan, and the Pakistani military is heavily engaged in responding to the needs that are generated by these floods," Mullen said after an appearance in Chicago. "In priorities right now, the Pakistani leadership, civil and military, as well as the Pakistani people, have to take care of the floods."

Other U.S. officials cautioned that Pakistan's army will be stretched thin by flood relief efforts for at least several more weeks.

The United States wants Islamabad to expand its pursuit of insurgents farther into North Waziristan, a border area next to Afghanistan often described as lawless. U.S. officials are hoping for assurances that Pakistan will not rule out that expansion because of the demands of flood relief.

Two U.S. officials spoke on condition of anonymity to describe the delicate military relationship with Islamabad.

On Tuesday, Marine Commandant Gen. James Conway said Pakistan's powerful Army chief, Gen. Ashfaq Pervez Kiyani, had warned him that the Army was preoccupied.

"The Pakistani leadership is consumed with responding to the aftermath of the flood disaster," Conway said at the Pentagon. Conway spoke a day after a trip that included a tour of flooded areas in Pakistan.

"Gen. Kiyani cautioned me that the involvement of his Army in the flood relief will for a time detract from their efforts to secure the Pakistani frontier," Conway said.

The United States has been the most generous contributor to the flood aid, rushing in emergency assistance to support a vital ally in the war against Al Qaida and the Taliban. But rebuilding Pakistan's devastated roads, power grid and other infrastructure will cost billions of dollars, and it is not certain where the money will come from.

The floods began almost a month ago with the onset of the monsoon and have ravaged much of the country, from the mountainous north through to its agricultural heartland. More than 8 million people are in need of emergency assistance, and more than 17 million have been affected.

The United Nations said some 800,000 people were trapped by the floods in areas accessible only by air. It said 40 more heavy-lift helicopters were urgently needed. The U.S. military has dispatched 19 choppers so far.

Nagata spoke to Pentagon reporters by video teleconference from Ghazi air base, where the United States is coordinating relief efforts.

He said U.S. troops are being received warmly in Pakistan, despite widespread anti-American sentiment there. He said there have been no threats or security problems for the approximately 230 U.S. troops involved in the aid effort.

A recent Pew Foundation poll found nearly six in 10 Pakistanis viewed the United States as an enemy; only one in 10 called it a partner.

The Associated Press contributed to this report.