London: US President Barack Obama arrived in London on Thursday with a mission - to persuade British voters not to ditch membership of the European Union in a referendum that Washington fears could weaken the West.
His visit is a welcome one for Prime Minister David Cameron, leading the "In" campaign, but has drawn scorn from those arguing that Britain should leave the EU.
Obama is likely to suggest Britons should vote to stay in the bloc to preserve Britain`s wealth, its "special relationship" with the United States and the cohesion of the West.
"As the president has said, we support a strong United Kingdom in the European Union," Ben Rhodes, Obama`s deputy national security adviser, told reporters in Washington before the trip.
After a visit to Saudi Arabia, including talks with King Salman, Obama arrived in London on Thursday.
The U.S. government - and many U.S. banks and companies - fear a Brexit would unleash market turmoil, diminish British clout, undermine London`s status as a global financial capital, cripple the EU and undermine Western security.
Opinion polls indicated that British voters are leaning towards the "In" camp in the June 23 referendum, but many remain undecided.
Asked about Obama`s views, Cameron told the parliament:
"Personally I believe we should listen to advice from friends and other countries and I struggle to find the leader of any friendly country who thinks we should leave."
Cameron has said that in the face of what he terms Russian President Vladimir Putin`s aggression, this is no time to drop out of the club Britain joined in 1973.
For Britain`s closest ally, EU membership amplifies British influence, facilitates trade for U.S. companies and strengthens the 28-member bloc which Washington views as a pillar of stability in the post-World War Two era.
Opponents of the EU - many of whom laud the U.S. alliance - say that membership has shackled Britain to the corpse of a failed German-dominated experiment in European integration and that Britain, if freed, could prosper as a sole trader.
New York-born Boris Johnson, the London mayor who heads the "Out" campaign, said he did not want to be lectured by Americans about EU membership.
"President Obama should butt out," Nigel Farage, another prominent opponent of EU membership, told Reuters.
"This is an unwelcome interference from the most anti-British American president there has ever been. Mercifully, he won`t be in office for much longer."
"Out" campaigners have said the United States would never agree to dilute its own national sovereignty in the way the EU requires of its member states.
Ahead of a 2014 Scottish vote on independence, Obama said he hoped Britain "remains strong, robust and united", a comment that was welcomed by unionist politicians in London.
Obama`s term in office ends next Jan. 20. On Friday he will have lunch at Windsor Castle with Queen Elizabeth, who celebrated her 90th birthday on Thursday, and her husband Prince Philip.
After lunch, Obama will hold talks with Cameron.