Scottish First Minister Alex Salmond has been forced to defend the release of the Lockerbie bomber Abdelbaset Ali Al Megrahi in the face of a blistering attack from the head of the FBI.
The leader of the Scottish National Party administration in Edinburgh said that they had made the “right decision” in freeing Megrahi on compassionate grounds after serving less than eight years of his life sentence.
He insisted that Scotland's relationship with the United States remained strong, despite the fury across the Atlantic that Megrahi would not now die in jail.
However, he came under fire from his Labour predecessor as first minister, Jack McConnell, who accused the SNP government of a “grave error of judgment” which had damaged Scotland's reputation.
In London, UK ministers expressed concern that the deepening row could have repercussions for wider British-US relations.
Jim Knight, Employment Minister, told Sky News' Sunday Live: “I hope there is no fall-out from this for Scotland, and I hope there is no fall-out from this for the UK in terms or our relationship with the US which is a key relationship for us.”
The depth of the anger in America was underlined by the letter from Robert Mueller, the Director of the FBI, to the Scottish Justice Secretary, Kenny MacAskill, who ordered Megrahi's release.
Mr Mueller, who was the US assistant attorney general responsible for the Lockerbie investigation, said he was outraged by the decision.
“Your action in releasing Megrahi is as inexplicable as it is detrimental to the cause of justice. Indeed your action makes a mockery of the rule of law,” he wrote.
“Your action gives comfort to terrorists around the world who now believe that regardless of the quality of the investigation, the conviction by jury after the defendant is given all due process, and sentence appropriate to the crime, the terrorist will be freed by one man's exercise of 'compassion'.”
Mr Salmond acknowledged the “hurt and disappointment” that had been felt in the US — from where most of the 270 victims came — but expressed his disappointment that Mr Mueller had failed to acknowledge that some of the families, particularly in the UK, had supported the release.
“No-one I think seriously believes we made any other decision except for the right reasons. I also absolutely know it was for the right reasons,” he said.
”The relationship between Scotland and the United States is strong, it is enduring, it is deep, and it cannot be based on always finding agreement.”
But with the recalled Scottish Parliament set to return today, a week early, to discuss the situation, Mr McConnell said the government needed to make it clear that the decision did not have the support of the people.
“I think it's absolutely vital that the Scottish Parliament now takes action to limit that damage and to give a clear indication to the rest of the world that when the Scottish Government made this decision they were not acting with the support of the people of Scotland,” he said.
Meanwhile, Gordon Brown continued to come under pressure from opposition parties to say whether he supported Megrahi's release. So far, UK ministers have refused to comment, sticking firmly to the line that it was a matter for the Scottish authorities.