WASHINGTON, US - The United States on Wednesday renewed its call for Sri Lanka to release more than 250,000 Tamil war refugees from their camps, warning of the potential for disease.

Heavy rains this week flooded nearly 2,000 makeshift shelters in the camps, where people displaced by war have been detained since the government in mid-May crushed the leadership of the Tamil Tiger rebels.

"Involuntary confinement is especially a source of concern given the recent rains and given the coming of the monsoon season," said Eric Schwartz, the US assistant secretary of state for population, refugees and migration.

"It makes it all the more important that release from confinement be an issue that friends of Sri Lanka continue to raise," he told reporters.

Sri Lanka says it needs time to weed out suspected rebel fighters from the camps to prevent a revival of the Tigers' four-decade struggle for an independent Tamil homeland, one of Asia's longest and bloodiest conflicts.

Schwartz, who visited a camp in Sri Lanka last month, said the conditions were "not great."

"There is concern about communicable diseases, especially when you're in a temporary facility," he said. "When things like rain happen, the trees get washed away and the potential for communicable diseases get much greater."

He said that a survey also showed a "relatively high" level of malnutrition among children, although he said part of the reason may have been the conflict itself rather than life in the camps.

Schwartz, speaking a day after he was formally sworn into office, said the United States was committing another 160 million dollars to international and non-governmental efforts on behalf of refugees and internally displaced people.

He said that 58 million dollars would assist refugees in Africa, particularly Somalia, with another 29 million assisting Afghan refugees, with the rest devoted to other areas around the world.