He is undergoing a course of chemotherapy, and that is all there is to say at this stage

Judy Daish Agent

He will still take part in two performances at the National Theatre as planned next week - but it is not known whether he will continue working after that.

Pinter is regarded by many as Britain's greatest living playwright and is also a respected stage director and has recently revived his acting career.

It has been reported that doctors told Pinter he had the disease about a month ago, but that he still felt strong.

Corin Redgrave will appear alongside Pinter at the National

He will continue to work on two performances of old sketches and mini-plays he is directing at the National Theatre, which will be staged on Friday, 8 February and the following Monday.

He is due to deliver a new monologue he has written, called Press Conference, alongside performances by Corin Redgrave, Patrick Marber, Frances de la Tour and Penelope Wilton.

But his agent Judy Daish told BBC News Online that she did not know whether he would take on any projects after that.

"He is undergoing a course of chemotherapy, and that is all there is to say at this stage," she said.

Pinter used to be a heavy smoker - one of the factors thought to contribute to cancer of the oesophagus.

John Thaw has also been treated for cancer of the oesophagus

It is the same disease that Inspector Morse actor John Thaw has undergone treatment for.

Born in London's East End, Pinter has recently continued to direct and act in the West End.

For the National's 25th anniversary, he has directed a revival of No Man's Land, which is still running and which is due to go on tour to Oxford and Newcastle in the next two months.

He also recently won acclaim for his role in another revival of one of his own plays, One for the Road.

His most important stage works include The Birthday Party - which was trounced by critics when it was first staged - plus The Caretaker, The Homecoming and The Betrayal.

Outspoken

He has also written screenplays and won awards including the Shakespeare Prize and the European Prize for Literature.

An outspoken political activist, he criticised allied bombing of Afghanistan after 11 September and was also a high-profile opponent of Nato bombing of Serbia.

But he has also been criticised by some who see him as a champagne socialist.

He is married to the historian and writer, Lady Antonia Fraser, his second wife.