Marshall Freeman Harris, the third official to quit in protest, launched a scathing attack on the integrity of Lord Owen as an impartial negotiator after spending three days in Geneva observing the peace talks at close quarters.
The former official, who until last week was the State Department's senior Bosnian expert, also demanded the immediate use of air strikes to roll back Serbian forces from Sarajevo and other Bosnian cities, and the introduction of American ground forces in Bosnia.
However, at a press conference in London, Mr Harris reserved his sternest criticism for Lord Owen and the international community for their unwillingness to force the Serbs to come to heel.
'We seem to have come to a point in the negotiations that Lord Owen and Karadzic's (the Bosnian Serb leader) aims have coincided,' he said. 'I think that Owen should be removed, in part because he seems only to want to reach a quick political settlement rather than a politically viable one.
'I can't for the life of me understand how an impartial negotiator can reject out of hand air strikes against the aggressor in this conflict and claim that they would interfere with reaching an agreement in Geneva,' he said.
He went on to say that Lord Owen was unjustly treating the Bosnian leadership as an equal partner in a three-way conflict.
'They are the principal victims in a war of aggression. He is not fulfilling his function as an impartial negotiator when he treats the Bosnian government neither as a legitimately elected government nor the victims.'
The aims of Western governments, Mr Harris said, appeared to be a solution which would establish mini- states across Bosnia that would ultimately lead to the uprooting of hundreds of thousands more people.
Mr Harris is not the only American voice to be raised in criticism against Lord Owen's peace-brokering efforts.
An article in the Washington Post newspaper this week called on him to resign 'rather than help dig the grave deeper for the victims of the Bosnian war'.
Its author, Jim Hoagland, wrote in a commentary: 'By asking the Bosnians to divide Sarajevo and give the Serbs control over part of their capital to get a truce, Lord David Owen has put an end to whatever good he could do for the people of ex-Yugoslavia or the international community.
'Creating a new Berlin Wall in the Balkans would not bring a durable peace.' He continued: 'The Bosnians are being asked in the Geneva peace talks headed by Owen not just to capitulate, but to acquiesce in the political destruction of the city they have bled and died to keep.'Reuse content