Martin McGuinness will refute first shot claim

"As far as I am concerned the British Army got away with murder on Bloody Sunday and they are presently trying to get away with murder at the tribunal," he said.

"The people of Derry are involved in a battle here with the British establishment and the British Ministry of Defence.

"The relatives are in the front line of that battle. The people who were injured are in the front line of that battle and I intend to stand with the people of Derry."

He added: "All we can say at this stage is that this is a very important tribunal and I will be giving my evidence and I do expect there will be criticism from the Unionists. How would it be any different?

At the weekend, Mr McGuinness met some of the families of those killed and wounded on Bloody Sunday to tell them about the evidence he is to give to the Saville Inquiry.

The tribunal sitting in the Guildhall in Derry is hearing evidence about the circumstances surrounding the events of 30 January 1972 when paratroopers opened fire on the marchers, killing 13 men.

'Unlocking the truth'

Northern Ireland Secretary John Reid said Mr McGuinness's decision to tell the inquiry of his role in the IRA marked a new openness in Northern Ireland society.

Dr Reid said it would be vital step towards unlocking the truth about the past.

"I welcome the fact that Martin McGuinness is to testify, first of all because I think it helps us to get at the truth of what happened, and also because I hope it does signal a new openness," he said.

First Minister David Trimble welcomed the statement by Mr McGuinness.

He said the political process was based on "the assumption that there is a transition and that people are changing" and were committing themselves to totally peaceful means.

Mr Trimble said he would be "delighted" if that could be proved through action by the IRA on arms decommissioning.

Sinn Fein's Mitchel McLaughlin said it was a significant development and had wide-ranging implications for the peace process.

'Nothing new'

Ulster Unionist Economy Minister Sir Reg Empey said the revelations about Mr McGuinness were "nothing new."

However, the Democratic Unionist Party have questioned Mr McGuinness's continuing role in the Northern Ireland Executive.

Gregory Campbell: "Questions should be asked about other IRA actions"

DUP Regional Development Minister Gregory Campbell said he had told the inquiry he was willing to give evidence himself.

In a 1984 BBC documentary he said he had evidence that Mr McGuinness had been actively involved in the IRA in the early days of the Troubles.

Speaking on BBC Radio Ulster on Monday, Mr Campbell said that if the IRA was acting under Mr McGuinness's instructions on Bloody Sunday, then questions must be asked about his role in IRA murders and violence in the days before.

People who give evidence to the inquiry can not be prosecuted on that evidence, however, Mr Campbell's party colleague Ian Paisley junior has called for Mr McGuinness to be arrested.

Ulster Unionist MP for East Londonderry, William Ross also said Mr McGuinness had many questions to answer.

Mr Ross said: "He has to be asked, did his duties involve overseeing terrorism or did it not?"

Agreement on 'peaceful march'

Mr McGuinness is expected to tell the tribunal that armed IRA members were standing by in the Creggan and Brandywell area of Londonderry during the march, but that it had been agreed by the organisation in advance that the city should be peaceful to facilitate a protest peaceful march.

Meanwhile, further discussions are expected on Monday about how soldiers who were involved in the Bloody Sunday operation in the Bogside, will give evidence.

The soldiers and former soldiers are resisting calls from relatives of those killed to come to Derry to give evidence in the Guildhall.

Chair of the inquiry Lord Saville of Newdigate is expected to ask them to give evidence via a video-link.

However, the soldiers have said revealing their identities would compromise their safety.

The original inquiry, which was rejected by the relatives as a whitewash, kept the soldiers' identities secret.

The tribunal has been sitting in public in Londonderry's Guildhall since March 2000.