President George W Bush [Images] said he is "pleased" with outgoing Under Secretary of State Nicholas Burns for agreeing to continue to handle the "historic" Indo-US civil nuclear deal in which Washington has been making "progress" under him.

"He (Bush) is pleased that under secretary Burns will continue to serve in an advisory capacity as the United States continues to make progress on the historic civilian nuclear agreement with India," the White House said in a statement.

Burns has been set with no time-line for completion of the deal with India and also no decision has been made to allot him the title of a 'special envoy' for the deal.

"No  timeline. I would expect it to continue as long as it's in the interests of the secretary to have Nick doing that," State Department spokesman Sean McCormack said.

"I don't know that we've settled on a title yet, but he will remain focused on that particular issue. I think he's uniquely positioned, given his role in negotiating," he said, adding that "Nick's one of these guys that manages to find 27 hours in the day".

While nominating the current American Ambassador in Moscow [Images], William Burns, to be the next Under Secretary of State for Political Affairs, Bush hailed services of the outgoing third-highest-ranking diplomat of the state department.

"As a career Member of the Senior Foreign Service for over two decades, under secretary Burns has worked tirelessly to help build a more democratic, secure and prosperous world.

"He has been at the forefront on key foreign policy issues for this administration, including negotiations on the civil nuclear cooperation agreement with India, discussions on Iran and the US-Israel Strategic Dialogue," the statement said.

"The president also appreciates Under Secretary Burns previous service as Ambassador to the North Atlantic Treaty Organisation, Ambassador to Greece, and for five years as an Adviser on Russian Affairs at the National Security Council beginning under President George H W Bush," it added.

Earlier, the surprise decision by 51-year-old Burns, who negotiated the deal for more than two years with the then Indian Foreign Secretary Shyam Saran, was announced by Secretary of State Condoleezza Rice, who asked the former to continue to handle the controversial deal which got bogged down in Indian politics.

"We have a lot of work to do. And I've asked Nick, also, that after he retires that he will spend some time continuing to work on the India file, particularly because we would like to push the US civil nuclear agreement to conclusion, if possible, and Nick has agreed to continue that work," she said.

"Obviously, when someone of Nick's caliber and quality decides to step down, you think mostly of what is going to be lost for the government, for someone who is such a committed person in carrying out the president's policies," Rice added.

Personal reasons were cited for the exit of Burns, who is expected to take up a job in the private sector. He was widely viewed as an experienced and skillful diplomat and also dubbed by some as the most gifted foreign officer of his generation.