Mr Buerk, 56, expects to leave by the end of the year.

His talents both as a newsreader and journalist are among the best in the business

Richard Sambrook Director, BBC News

He told BBC management of his decision on Thursday evening.

He has been one of the best known faces of BBC News for 20 years.

He will continue working as a presenter on BBC Radio Four, on news specials and possibly on assignments abroad.

"By November I will have presented the main evening news more than 4,000 times. It's more than enough," he said.

His coverage of Ethiopia's famine prompted Live Aid

He was praised for his "clarity, reliability and wonderful kind of familiarity" by BBC director of television, Jana Bennett.

Director of BBC News Richard Sambrook said Buerk had made "one of the most significant contributions to BBC journalism".

"His talents both as a newsreader and journalist are among the best in the business and I am delighted that he will continue to work with BBC News on current affairs projects and special news reports," he said.

Mr Buerk had planned to retire from news presenting in 2001 but was persuaded to stay on for one more year.

In that time the main evening news programme switched from its old nine o'clock slot to one hour later.

'Pressure'

Mr Buerk has reported for the BBC from more than 60 countries.

He won much praise for his coverage of the Ethiopian famine in 1984 but has been critical of the current pace of TV news reporting.

In 2000, he told the Radio Times that the "pressure to deliver" in such situations made it hard to pursue stories properly.

He noted a growing trend for news coverage to be focused on the "superficial and ephemeral".