Seif al-Islam Gadhafi, son of Libyan leader Moammar Gadhafi, gestures as convicted Lockerbie bomber Abdel Basset Ali al-Megrahi, left, arrives at an airport in Libya on Thursday. (Associated Press)

The U.S. State Department has given Scotland assurances that despite disagreeing with the compassionate release of Lockerbie bomber Abdel Basset Ali al-Megrahi, it will not affect relations with Britain.

The U.S. will stand by Britain even though it believes the decision to release al-Megrahi was a mistake, State Department spokesman Ian Kelly said Monday.

"We made it quite clear that we disagree passionately with this decision because we thought it sent the wrong signal to not only the families but also to terrorists," Kelly said.

However, there will not be "tit-for-tat retaliation" against the U.K. because of the decision, Kelly said.

Questions have been raised about the British government's involvement in his release, with some saying the U.K. approved the move to boost business ties between Britain and Libya, which has vast oil reserves.

But Kelly said the U.S. has no evidence the Scottish decision was based on economics, and believes officials who said it had nothing to do with business ties with Libya.

Scotland has faced criticism from the U.S. government and the families of American victims of the 1988 airline bombing for al-Megrahi's release.

In a strongly worded letter to the Scottish government on the weekend, FBI director Robert Mueller said al-Megrahi's release gave comfort to terrorists; Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, said releasing the bomber was "obviously a political decision."

Decision defended

Scottish officials have maintained there are differences between the British and American judicial systems and on Monday Scottish Justice Secretary Kenny MacAskill stood by his controversial decision.

Scotland's Justice Secretary Kenny MacAskill gestures during a special parliament session to discuss the recent release of Libyan Abdel Basset Ali al-Megrahi. (David Moir/Reuters)"I believe that I followed due process and I upheld the values [of Scotland] and I stand by my decision," MacAskill told Scottish legislators on Monday after the Scottish Parliament was recalled to discuss the issue.

Some Scottish legislators have called for MacAskill to resign for his decision to release al-Megrahi, who is terminally ill with prostate cancer.

Opposition politicians have also threatened to hold a no-confidence vote due to the decision, which could potentially bring down the minority government.

MacAskill said the decision was not based on political, economic or diplomatic considerations but that he was following due process, and that he included the opinions of social work staff, medical experts and the parole board, who all recommended compassionate release.

"No compassion was shown by him to [his victims] but that alone is not a reason to deny compassion to him and his family in his final days," he said.

MacAskill announced the decision to release al-Megrahi last Thursday, saying it was based on Scottish law that entitles a prisoner to be considered for compassionate release if his or her death is believed to be imminent.

"Last week, the Scottish government made a wrong decision in the wrong way with the wrong consequences," Labour legislator Iain Gray told parliament during the emotional debate on Monday.

The Scottish people were ashamed "to see our flag flying to welcome a convicted bomber home," Gray said.

Hero's welcome

The hero's welcome al-Megrahi received on his return to Libya has been condemned by Britain and the U.S.

MacAskill said the reception al-Megrahi received was regrettable but that the Libyan government had given assurances that any return would be dealt with in a low-key manner. But he made no apologies for the release of al-Megrahi.

"I do fully accept that Mr. al-Megrahi showed neither compassion for the perpetration of the atrocity nor indeed sensitivity when he was shown compassion by us," MacAskill said.

"But I reiterate that I stand by the values that we have."

Al-Megrahi, 57, was sentenced to life in prison for his role in the 1988 bombing of Pan Am Flight 103, which exploded over the Scottish town of Lockerbie on Dec. 21, 1988.

The former Libyan secret service agent is the only person ever convicted in the bombing. All 259 people aboard the London-to-New York flight and 11 people on the ground were killed, including two Canadians. Most of the passengers were Americans.

With files from The Associated Press