The administration of US president Barack Obama is to announce the deployment of an additional 40,000 troops to Afghanistan, according to the Afghan ambassador to Washington, as the US steps up its efforts to contain the growing Taliban insurgency.

The move would be controversial in Washington, where some influential politicians, led by Joe Biden, the vice-president, are at odds with General Stanley McChrystal, the US's senior commander in Kabul, who has publicly requested tens of thousands more troops.

“The indications are that the president will comply with the demands of Gen McChrystal and the number he is asking for is more than 40,000,” Said Jawad, the Afghan ambassador to Washington, said yesterday, citing conversations with officials from the Pentagon and other government departments.