Rescue workers in northwest Pakistan are struggling to reach thousands of villagers who are stranded by flooding that has killed more than 1,000 people.

A week of heavy rain caused what officials say is the worst flooding on record in Pakistan, with the province of Khyber Pakhtunkhwa being the hardest hit.

Pakistani officials say the death toll rose to 1,100 Sunday, but they say the number could continue to increase because of the widespread devastation.

Thousands of homes and vast swaths of farmland have been destroyed in the region. The United Nations estimates that one million people across Pakistan have been affected by the disaster.

Officials also say they fear an outbreak of waterborne diseases like diarrhea and cholera among survivors.

The U.S. embassy in Islamabad announced Sunday that the United States will provide $10 million in humanitarian assistance. The embassy says it already has provided 50,000 meals for people in the affected areas, as well as helicopters to help with the rescue effort.

Officials say Pakistani troops have rescued about 19,000 people, many of them trapped on rooftops.

Meanwhile, in neighboring Afghanistan, flood waters have killed more than 60 people.

Afghan and NATO forces said they were using helicopters to conduct rescues and distribute aid to the worst-affected regions of Afghanistan, including Kunar and Nangarhar provinces.

Some information for this report was provided by AP, AFP, Reuters.