Scottish Justice Secretary Kenny MacAskill has defended his decision not to attend a US Senate hearing on the release of the Lockerbie bomber.
He said he was "accountable to Scotland" and had "no information to provide" on any BP oil deal.
Former UK Justice Secretary Jack Straw has also declined an invitation to attend the hearing.
Senators want to examine claims BP may have lobbied for the release of Abdelbaset Ali al-Megrahi.
Mr Straw announced he would not be attending the hearing after saying he could not answer the central question about why the Scottish government decided to release Megrahi.
In a letter to the US Senate foreign relations committee explaining why he would not give evidence next Thursday, Mr Straw said he had "absolutely nothing to do with the decision" to release Megrahi.
He added: "I saw no papers about it, and was not consulted about it. Indeed I was on holiday at the time and only learnt about it from an item on the BBC News website.
"I believe that Mr MacAskill has confirmed that the decision was one taken entirely on medical grounds, without involvement from the UK government, and without pressures from BP."
Oil giant BP said it was considering its course of action after also receiving an invitation to give evidence to the committee.
The Scottish Prison Service's medical chief Dr Andrew Fraser was also invited to the hearing, but has declined.
Mr MacAskill said the Scottish government was co-operating fully with the US Senate and denied he was "running scared".
He said: "The US Senate's invitation is primarily predicated on an investigation into what may or may not have happened with regard to a BP oil deal.
"The Scottish government was neither party nor privy to what was going on there, so we've made it quite clear that we have no information that we can provide regarding that.
"If there is any information on points, we are happy to clarify matters but we really can't be of any assistance on that."
He said it was "proper form" for him to give evidence to Holyrood and to Westminster - but not to the US Senate.
He said: "I'm the cabinet secretary for justice.
"I am accountable to the Scottish Parliament and I'm elected by the Scottish people.
"That's why when I was asked to appear before a Scottish Parliamentary committee on Megrahi, I did so, and that's proper form."
He said he could not assist the US Senate's inquiries regarding BP.
However, his decision not to attend has been criticised by Labour's Holyrood justice spokesman Richard Baker.
He told BBC Radio Scotland's Good Morning Scotland: "It speaks volumes about the lack of confidence he has now in his own decision that he is running a mile from any scrutiny of it."
Mr Baker argued it was "perfectly legitimate" for American politicians to ask Mr MacAskill to come to Washington and answer questions, saying the senators "represent so many of the families who lost loved ones" in the atrocity.
US senators have called for a full inquiry into claims which recently resurfaced that BP had lobbied the UK government for Megrahi's release from a Scottish jail.
BP has confirmed it did press for a prisoner transfer agreement with Libya because it was aware that a delay might have "negative consequences" for UK commercial interests.
However, the firm has said it was not involved in any discussions regarding Megrahi's release.
The Libyan convicted of the 1988 atrocity in which 270 people were killed was freed by Mr MacAskill on medical grounds last August.