Sir John Scarlett, chairman of the Joint Intelligence Committee (JIC), which coordinates the work of Britain's intelligence agencies, was to appear before the inquiry headed by Lord Brian Hutton.

The 30-year MI6 veteran was due to be grilled on what political pressure, if any, he came under during the preparation of a September 2002 dossier on Iraq and weapons of mass destruction -- a key plank in Blair's case for taking Britain to war.

Kelly was the source of a BBC report in May alleging that Downing Street "sexed up" the dossier, which notably claimed that Saddam Hussein could deploy chemical or biological weapons in as little as 45 minutes.

Blair is to testify on Thursday, on the heels of his defence minister Geoff Hoon, who many observers believe could wind up losing his job as a result of the controversy.

The British prime minister ordered the judicial inquiry on July 18 just hours after the body of Kelly -- a one-time UN arms inspector in Iraq and one of the world's top authorities on Saddam Hussein's secret arsenals -- was found in woodland near his home in the English countryside, west of London.

Over the weekend, the inquiry released 9,000 pages of documents, including notes of government meetings which suggested that Blair was intimately involved in deciding whether Kelly should be exposed as the anonymous source behind the original May 29 BBC radio report on the September dossier.

As well as being asked about his role in drawing up the dossier -- he has insisted he was happy with its contents -- Scarlett was likely Tuesday to face questions about what advice he gave about the handling of Kelly.

Among the documents released over the weekend included one detailing a meeting in Blair's office, in which Scarlett asked: "If Dr K's name becomes public, will government be criticised for putting him under 'wider pressure'?"

Although the evidence to be given Tuesday was sure to be of interest, the main events this week will be Wednesday's appearance by Hoon, followed Thursday by the prime minister.

When the inquiry began three weeks ago, it was expected that Blair would not be heard before the middle or end of September. It is Hutton, a former Northern Ireland chief justice, who picks the order in which witnesses appear.

Having returned from his summer holiday in Barbados, Blair spent the weekend at his country residence at Chequers, outside London, being briefed by lawyers on his evidence to the inquiry.

Some 40,000 British troops joined the US-led war on Iraq after Blair's government published dossiers in September 2002 and February 2003 to convince a skeptical parliament and public that firm action was needed to confront Saddam.