The United States on Friday slammed the release of Lockerbie bomber Abdelbaset Ali Mohmet al-Megrahi from a Scottish prison one year ago as "unfortunate, inappropriate and wrong."
"Today is the one-year anniversary of the unfortunate, inappropriate and wrong decision by the Scottish executive" to free Megrahi, said President Barack Obama's counter-terrorism adviser, John Brennan.
"We've expressed our strong conviction that al-Megrahi should serve out the remainder, the entirety of his sentence in a Scottish prison. We will continue to reiterate this position to the Scottish and Libyan authorities," he said.
Obama "extends his deepest sympathies to those affected by that reprehensible act of terrorism," Brennan told reporters.
His comments, made as Obama enjoyed a 10-day family vacation on this resort island, came after US Secretary of State Hillary Clinton said Washington "continues to categorically disagree with the decision" to free Megrahi.
"As we have expressed repeatedly to Scottish authorities, we maintain that al-Megrahi should serve out the entirety of his sentence in prison in Scotland," Clinton said in a statement.
"We have and will continue to reiterate this position to the Scottish and Libyan authorities. We extend our deepest sympathies to the families who lost loved ones and share their desire for justice to prevail," she said.
The remarks from Brennan and Clinton came amid calls from four US senators for a new investigation into whether business considerations played a role in the decision to let Megrahi return to his homeland of Libya.
The lawmakers have suggested that embattled oil giant BP might have lobbied for his release in order to safeguard a 900-million-dollar oil exploration deal with his Tripoli, a charge Scottish and British officials have denied.
Megrahi was thought to have only three months to live because of terminal prostate cancer when he was released on compassionate grounds and returned to his homeland Libya to a hero's welcome - but has confounded that diagnosis.
Megrahi remains alive today, to the dismay of mainly American relatives of the 270 people who died when Pan Am Flight 103 blew up over the Scottish town of Lockerbie, four days before Christmas in 1988.
"We certainly take umbrage at that reference to compassion, because Megrahi did not have any compassion at all for those victims," said Brennan.
The United States opposed the decision by Scotland's devolved government to free Megrahi, and the US Senate unanimously approved a resolution in September 2009 denouncing the move and what lawmakers condemned as his "hero's welcome" in Libya.
Democratic Senators Robert Menendez and Frank Lautenberg of New Jersey and Chuck Schumer and Kirsten Gillibrand of New York have stepped up calls for a new investigation since mid-July.
On Friday, the lawmakers unveiled a new letter to leaders of Scotland, Libya and Qatar seeking information and a new probe into whether trade issues swayed the decision to release the bomber and calling into question the stated medical justification.
"Many questions have been raised as to whether the doctors who Scottish authorities consulted believed at the time Mr Al-Megrahi had only three months to live," they wrote.
"Because these questions remain open, the families of the victims of Pan Am Flight 103 remain concerned that commercial concerns between Scotland, Qatar, and Libya played a role in Mr al-Megrahi?s release," they said.
The letter underlined that Scotland had sought financing from Qatar for public works projects, and that top Qatari officials had discussed Megrahi's situation with Scottish officials.
And one of Libyan strongman Moamer Kadhafi's sons, Saif Al-Islam Kadhafi, "stressed that the release was crucial for future cooperation, including with BP. We intend to get a whole picture of what happened," said Menendez.
Menendez was due to chair a US Senate foreign relations committee hearing into the issue after lawmakers return to work September 13.