Washington (CNN) -- Prime Minister David Cameron makes his first White House visit as Britain's leader Tuesday.
Cameron became prime minister in May. Topics he is expected to discuss President Barack Obama will include the war in Afghanistan and last year's release by Scotland of the Libyan man convicted in the 1988 Lockerbie airplane bombing, White House Press Secretary Robert Gibbs said Monday.
Britain is a leading ally in the U.S.-led military coalition fighting Taliban insurgents in Afghanistan. However, Cameron is under pressure at home to end the British involvement in the campaign.
"I think the president has, on a number of occasions, laid out why what he's doing in Afghanistan is in our national security interests. We will continue to make that case tomorrow," Gibbs told a news briefing. "Obviously, we have, in both this administration and in the previous administration, had the help of the British government. I think both they and we have said we will not be there forever."
Gibbs also said the release last August of Abdelbaset Ali Mohmed al Megrahi, who was sentenced to life for his role in the bombing of Pan Am Flight 103 over Lockerbie, Scotland, would come up at Tuesday's meeting. The Pan Am bombing killed 270 people, most of them Americans.
The Scottish government released al Megrahi on compassionate grounds after doctors said he had terminal prostate cancer and just three months to live.
Al Megrahi is still alive, and news reports in recent days have questioned whether he was as sick as depicted. Questions also have been raised about whether a deal was cut to release him to protect British business interests in Libya, with oil giant BP exerting influence in the case.
"This issue will come up, and again, I would reiterate that it was our strong belief then and it continues to be our strong belief now that the Lockerbie bomber should not have been released," Gibbs said.
Secretary of State Hillary Clinton and four U.S. senators have called for Britain to revisit the case, even though there is little chance that al Megrahi could be returned to custody from his native Libya.
The four senators -- from New Jersey and New York -- also have requested a meeting with Cameron on al Megrahi's release and a possible BP role in it. Cameron has cleared his schedule to meet with the lawmakers, the British Embassy said late Monday night.
"The prime minister recognizes the huge strength of feeling on this issue and has immense sympathy for the families -- American, British and others -- affected by the Lockerbie atrocity," said Martin Longden, the press secretary at the embassy. "He has been very clear that the decision to release Megrahi was a mistake which he opposed at the time. The prime minister has personally asked to rearrange his program in Washington to enable him to meet with the four senators and discuss their concerns directly. The embassy has written to the senators tonight to invite them to the British ambassador's residence tomorrow evening."
Gibbs played down any possible tension between Obama and Cameron over the role of BP -- a British company - in the Gulf of Mexico oil disaster.
"The president is certainly looking for BP to live up to its monetary obligations to pay the damages and the fines that it will be assessed as a result of this disaster, and I think that's what the prime minister has said as well," Gibbs said.