US senators' interest in the Lockerbie bomber's release has "waxed and waned", a spokesman for First Minister Alex Salmond said ahead of a meeting on the issue.
Justice officials from the Scottish Government will hold talks in Edinburgh with representatives of a US Senate committee investigating the release of Abdelbaset Ali Mohmed Al Megrahi last year.
The Senate Foreign Relations committee is to hold a hearing on the bomber's release, chaired by Democratic Senator Robert Menendez, and US officials will meet justice representatives from the Scottish Government.
The US politicians want to investigate concerns that the bomber's release was linked to an oil deal - a suggestion strongly denied by all parties involved.
A spokesman for Mr Salmond said: "It was the First Minister who revealed to the world that the UK Government and the Libyan Government were planning or negotiating a prisoner transfer agreement clearly with the specific purpose of Al Megrahi being transferred to Libya. We've looked at all the records and asked the senators for them to furnish us with any public comment they issued at that time - there was no public comment.
"Senator Menendez and his colleagues' interest in the matter certainly seems to have waxed and waned. It seemed to be non-existent at the time when it was revealed to the world there was this 'deal in the desert'."
The UK Government has rejected requests to meet with US officials. One is a staff member of committee chairman Sen Menendez and another is an official of the committee.
Justice Secretary Kenny MacAskill has met with a number of members of congress in recent months on the issue.
Megrahi is the only person to be convicted of the 1988 bombing of Pan Am Flight 103 over Scotland, in which 270 people died - most of them Americans.
Mr MacAskill released the Libyan on compassionate grounds after he was given three months to live but he remains alive. His release 13 months ago sparked fury in America and has been condemned by President Barack Obama's administration.