WASHINGTON - Pakistan has assured the United States it will press its campaign against insurgents inside its borders despite the extraordinary demands the devastating floods have inflicted on its military, U.S. officials said Wednesday.

The U.S. military official leading the U.S. flood relief mission in Pakistan said he is confident that Islamabad will 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," said Brig. Gen. Michael Nagata.

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.

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 Qaeda and 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 U.S. 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.

Before the disaster, the U.S. had pledged to spend $7.5 billion over the next five years on projects including improving schools and hospitals, building dams and helping the country generate electricity.

The Pakistan government says about $800 million in emergency aid has been committed or pledged so far. But there are concerns in the international community about how the money will be spent by the government, which has a reputation for inefficiency and corruption.

The U.S. interest in helping goes beyond easing suffering. Washington does not want Pakistan's weak civilian government to lose ground to Muslim charity groups associated with militants, who are also providing aid to flood victims.

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.