UNITED NATIONS, Dec 4: The controversial US Ambassador to the United Nations, John Bolton, has tendered his resignation and will step down at the end of this year, US officials said.

The White House also announced on Monday that a formal announcement would be made by President Bush.

Mr Bolton's nomination has languished in the US Senate Foreign Relations Committee for more than a year, blocked by Democrats and several Republicans.

Senator Lincoln Chafee, a moderate Republican who lost in the midterm elections on Nov 7 that swept Democrats to power in both houses of Congress, was adamantly opposed to Mr Bolton.President Bush gave Mr Bolton the job temporarily in Aug 2005, while the Congress was in recess. But the appointment expires when Congress formally adjourns, no later than early January.

The White House resubmitted Mr Bolton’s nomination last month. But with Democrats capturing control of the next Congress, his chances of winning confirmation appeared slight.

The incoming chairman of the Senate Foreign Relations Committee, Democratic Senator Joe Biden of Delaware, said he saw no point in considering Mr Bolton's nomination again.