American news anchor Peter Jennings has been diagnosed with lung cancer.

The reporter, who hosts the World News Tonight programme for ABC, had been feeling ill for the past few weeks.

He revealed his condition to ABC News staff in an email this morning. "It was quite a surprise," Jennings wrote. "As you all know, this is a challenge. I begin chemo-therapy next week. I will continue to do the broadcast. There will be good days and bad, which means that some days I may be cranky and some days really cranky!

"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. In all the years I have worked here I have had the most outstanding support from this news division. Hundreds of you have been like family. It feels good to have such a family right now."

Jennings was last seen on screen on Friday but, according to TV Newser, will be back in the anchor seat for tonight's (Tuesday) show. World News Tonight is broadcast in the UK on BBC News 24.

In a later email to staff, ABC News president David Westin said: "This morning, Peter Jennings told his senior staff at World News Tonight that yesterday afternoon he was diagnosed with lung cancer. I include below the full text of Peter's note to the group of people with whom he works most closely. He will begin outpatient treatment next week here in New York. It's both Peter's and my expectation that he will anchor World News Tonight during the period of treatment to the extent he can do so comfortably; but, we should also expect him to be off the broadcast from time to time, depending on how he feels. Charlie Gibson, Elizabeth Vargas, and others will be substituting for Peter as necessary and when their other responsibilities permit.

"All of us at ABC News have watched over the years as Peter has led us on various assignments with strength and with courage. We've done our best to support him in these endeavors. Now, Peter's been given a tough assignment. 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. I know that all of us will give him every bit of support that he needs and asks for. Peter will once again lead the way, but we will stand with him at every turn."

Jennings, 66, has been with the network since 1964. During his time, he has covered both the rise and fall of the Berlin wall and is considered one of the most influential TV journalists in the US.