John Brennan, President Barack Obama's counterterrorism adviser, told reporters accompanying the vacationing leader that the U.S. has "expressed our strong conviction" to Scottish officials that Abdel Baset Al-Megrahi should not remain free. The comments came on the first anniversary of Al-Megrahi's release.
Brennan criticized what he termed the "unfortunate and inappropriate and wrong decision," and added: "We've expressed our strong conviction that Al-Begrahi should serve out the remainder - the entirety - of his sentence in a Scottish prison."
Earlier in Washington, Secretary of State Hillary Rodham Clinton issued a statement that underscored the U.S. position.
Similarly, he said the U.S. had "effective and productive discussions" with Libyan officials since the restoration of full diplomatic relations two years ago.
"We will use those diplomatic channels to convey our sentiments on a broad range of issues to include Mr. Al-Megrahi," said Brennan.
Al-Megrahi was ordered in 2001 to serve 27 years in prison for the bombing over Lockerbie, Scotland, but was freed on Aug. 20 of last year on compassionate grounds. He was said to suffer from cancer and had just months to live.
The bombing killed 259 people onboard - mostly Americans - and 11 on the ground.