Peter Jennings told staff at ABC World News Tonight that he was diagnosed with lung cancer Monday.

NEW YORK (CNN/Money) - Peter Jennings has been diagnosed with lung cancer but will continue to host "World News Tonight," ABC News said Tuesday.

The 66-year-old Jennings, who has anchored ABC's flagship newscast since 1983, told senior staff at "World News Tonight" in an e-mail obtained by CNN that he was diagnosed Monday afternoon.

Jennings planned to address his diagnosis on the broadcast Tuesday evening.

"He had been feeling ill for the last couple of months," an ABC News spokesman said. "He did not travel to cover the tsunami. The symptoms persisted, he went for further tests and the diagnosis was made."

"Almost 10 million Americans are living with cancer. I am sure I will learn from them how to cope with the facts of life that none of us anticipated," Jennings said in his e-mail.

Jennings will begin chemotherapy next week in New York, ABC News President David Westin said in a separate e-mail to ABC staff.

"Now, Peter's been given a tough assignment," wrote Westin. "He's already bringing to this new challenge the courage and strength we've seen so often in his reporting from the field and in anchoring ABC News."

Charlie Gibson, Elizabeth Vargas and others will substitute for Jennings as necessary, Westin said.

Jennings joined ABC News on Aug. 3, 1964. Prior to his current position, Jennings served as the anchor of the "ABC Evening News" and was the chief foreign correspondent for ABC News and the foreign desk anchor for "World News Tonight."

Jennings is the fourth high-profile broadcast news anchor to make headlines in the last year.

Just last week, Ted Koppel announced he was leaving ABC and the "Nightline" show he hosted since it started in 1980.

Long-time NBC News Anchor Tom Brokaw also retired in December, and CBS News Anchor Dan Rather gave up his anchor post in March, following a controversy involving a 2004 CBS News report based on forged documents related to President Bush's military service. Rather is still employed by CBS.

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