An offer of aid from the Venezuelan president, Hugo Chávez, which included two mobile hospital units, 120 rescue and first aid experts and 50 tonnes of food, has been rejected, according to the civil rights leader, Jesse Jackson.

Mr Jackson said the offer from the Venezuelan leader, whom he recently met, included 10 water purification plants, 18 power generation plants and 20 tonnes of bottled water.

The offer was made in a letter from the Venezuelan ambassador to the United States, Bernardo Alvarez, to the governor of Louisiana, Kathleen Blanco.

It was one of many from governments and aid organisations across the world, despite allegations by many conservative commentators and bloggers that the US is being ignored by countries it has helped during crises.

Mr Jackson said the rejection of the offer from one of Mr Bush's most outspoken political foes was a sign the federal government was incapable of handling the crisis properly. "This may be Mr Bush's worst hour of leadership," said Mr Jackson.

Other nations have been providing aid: Greece has offered cruise ships to help house evacuees; Sweden is making aircraft available to transfer supplies; El Salvador has offered troops ; Russia and Switzerland are providing generators, tents and meals. Other countries are sending people to assist in search-and-rescue: France and Latvia have sent teams with experience in disaster areas and the Norwegian navy was sending divers. Britain and Germany have sent relief experts and food rations.