Dr Khalilzad is the administration's senior Afghan-American

In a statement, the White House said Dr Khalilzad would be a special presidential envoy for Afghanistan, liaising with the Afghan people as they prepared to consolidate a new order.

He is already the most senior Afghan-American working in the current administration, and starts his new job almost immediately.

He is now preparing a visit of around two weeks to the region, first to the key US ally, Uzbekistan, then going on to Afghanistan before visiting Pakistan and India.

But he will be based in the US, continuing to head the National Security Council team on south-west Asia, the near-east and North Africa.

Regional expertise

Mr Khalilzad's detailed knowledge and understanding of the country must have already played an important role in the shaping of policy in the region.

Throughout the 1990s, he had warned in academic papers that the US needed to pay more attention to the problems of Afghanistan.

More recently, he played an important part in developing the defence strategy of the Bush administration, both before and after the September the eleventh attacks.

His knowledge of the region and local languages will undoubtedly give him added credibility as he starts the delicate task of helping Afghanistan recover from more than two decades of warfare.