A hearing of the United States Senate Foreign Relations Committee into the early release of the Lockerbie bomber has been postponed.
It had been scheduled for Wednesday.
The committee is looking into whether BP sought the release of Abdel Baset al-Megrahi to help get a $US900 million exploration agreement with Libya off the ground.
BP acknowledges it urged the British government to sign a prisoner transfer agreement with Libya, but stresses it did not specify al-Megrahi's case.
Senator Robert Menendez who was to chair the Senate hearing said on Tuesday he had been forced to re-schedule because key witnesses including former BP chief Tony Hayward and former British Justice Secretary Jack Straw were refusing to appear.