Lord Owen helped draw up the Vance-Owen peace plan
Former peace envoy David Owen has told the international war crimes tribunal that former Yugoslav President Slobodan Milosevic failed to use his power to end fighting in the Balkans.
Lord Owen, who mediated in Balkans peace negotiations between 1992 and 1995, told The Hague tribunal Mr Milosevic had "strong power" over rebel Serbs in Bosnia and Croatia at the time of the 1993 Vance-Owen peace plan.
He said Mr Milosevic "was in charge of a government that could stop them from shelling Sarajevo, stop ethnic cleansing".
"If he would have done that, it would have brought peace to Bosnia two years earlier," he said.
But Lord Owen also gave some support to Mr Milosevic's claims that he had less control by the time of the massacre of thousands of Muslims in Srebrenica in 1995.
Mr Milosevic faces a genocide charge for the Srebrenica massacre among 66 charges of war crimes, crimes against humanity and genocide.
Lord Owen, 65, helped draw up the Vance-Owen peace plan to end fighting between Bosnian Serbs, Muslims and Croats in January 1993.
The proposal, which would have divided Bosnia into 10 ethnic regions, was accepted by the Bosnian Muslims, but rejected by the Bosnian Serbs.
Lord Owen told the tribunal Mr Milosevic appeared to have had power to stop fierce fighting and implement peace, but failed to do so.
Milosevic's influence had waned by 1995, said Owen
"I believe he did have that power," he said.
"I know at times he felt he didn't, but at that time his power and influence over the Bosnian and Croatian Serbs was strong.
"It was a massive mistake not to use his power to impose upon the Serbs those settlements."
Lord Owen continued: "Pressure should have come from Milosevic... but it also should have come from the West.
"The responsibility was shared... but the greatest responsibility was for the people of the former Yugoslavia who should have behaved differently."
Lord Owen also described Mr Milosevic's character to the court.
"He is not fundamentally a racist," he said. "He is a nationalist, but that he wears lightly. He is a pragmatist."
Asked whether Mr Milosevic had lied to him during the talks, Lord Owen said that one of the saddest aspects of the talks was that there was practically no one who could be relied on to tell the truth.
Mr Milosevic, during his cross-examination of Lord Owen, said he had tried to use his "influence" to end fighting in Bosnia.
"Quite obviously that influence was not enough," he said.
But Lord Owen said he had urged the Yugoslav president "time and time again" to cut off fuel supplies and ammunition to Bosnian Serbs to force them to stop fighting.
The BBC's Geraldine Coughlan in The Hague said the cross-examination was a respectful exchange between the two men.
Lord Owen also told the court that Mr Milosevic had told him in 1993 that "if the Bosnian Serb troops entered Srebrenica there would be a bloodbath because of the tremendous bad blood that existed between the two armies".
Two years later, more than 7,500 unarmed Muslims men and boys were massacred by Bosnian Serb troops in Srebrenica
Mr Milosevic denies allegations that he controlled Bosnian
Serbs who carried out a widespread persecution of Croats
and Muslims in Bosnia.
Lord Owen, whose testimony is expected to last two days, is an independent witness as he wanted to be called by the court so as to preserve the impartial position of international negotiators.
The trial was adjourned until Tuesday.