U.S. Army choppers carrying emergency food and water buzzed over the swollen Swat River and washed-out bridges, landing in the valley once controlled by the Taliban. They returned laden with grateful Pakistani flood survivors — newly won friends in a country where many regard America as the No. 1 enemy.

KALAM, Pakistan — U.S. Army choppers carrying emergency food and water buzzed over the swollen Swat River and washed-out bridges, landing in the valley once controlled by the Taliban. They returned laden with grateful Pakistani flood survivors — newly won friends in a country where many regard America as the No. 1 enemy.

With Pakistan reeling from two weeks of flooding that has killed 1,500 and affected nearly 14 million people, the aid and rescue mission by the U.S. military gives the U.S. a chance to strengthen a sometimes troubled alliance that is crucial to fighting militancy in the region and ensuring a stable Afghanistan.

Besides helping those trapped by the high water, the U.S. assistance already is having another effect: The Pakistani Taliban denounced it and urged a boycott of Western aid.

Other U.S. relief missions to disasters in the Muslim world — including the 2005 earthquake in Pakistan-controlled Kashmir and the 2004 tsunami in Indonesia — were credited with improving the image of the United States, at least in the short term.

Now, as U.S. troops work side by side with Pakistani forces, the mission may relieve some pressure on the civilian government in Islamabad. President Asif Ali Zardari, who returned Tuesday to Pakistan, has been criticized for being abroad since Aug. 1, amid one of the worst natural disasters in his country’s history.

The United Nations said hundreds of millions of dollars in international assistance would be needed. In Washington, the State Department announced an additional $20 million in flood relief, bringing the total U.S. aid in the crisis to $55 million.

A spokesman for the Pakistani Taliban, which has attacked international aid workers in the past and has long opposed foreign assistance, said it would fund relief efforts.

The foreign aid “is deceiving the nation. It will not reach the affected people, but will be pocketed by corrupt rulers,” said Azam Tariq, adding the disaster was God’s punishment to Pakistanis for accepting secular leaders.

Highlighting the stakes for Pakistan and the United States is the quick work in badly affected areas by hard-line Islamist charities, including one with alleged militant links. With civilian authorities overwhelmed, concerns are rising the disaster will build support for the extremists, and perhaps even undo recent security gains.

The U.S. assistance is focused on the Swat Valley, which was under Taliban control until a Pakistani army offensive last year. Since then, it has been trying to rebuild with the help of the international community, which does not want the militants to return.