US President Barack Obama has arrived in Germany to hold talks with German Chancellor Angela Merkel, one of his closest allies in dealing with a shaky global economy and security crises in the Middle East and Ukraine.
It will be the last stop on a six-day foreign journey where Mr Obama has sought to shore up US alliances he views as key to increase trade, defeat Islamic State militants and offset Russian intervention in Ukraine and Syria.
Mr Obama, who is in the last nine months of his presidential term, spent three days in London where he urged Britons to remain in the European Union in a June referendum, a vote that could have global economic consequences.
He warned it could take a decade for the UK to negotiate a new trade agreement with the United States if it leaves the European Union.
In a BBC interview, Mr Obama said "it could be five years from now, 10 years from now before we were able to actually get something done".
"Our preference would be to work with this large bloc of countries," he added.
Nigel Farage, leader of the anti-EU UK Independence Party, said that "Barack Obama is not a pro-British president".
But Mr Obama told the BBC that he hoped British voters would listen to the friendly opinion of "the President of the United States, who loves the British people and cares deeply about this relationship".
And he said the close relationship between Britain and the US would endure, whatever happened.
"The bond between our two countries is unbreakable," Obama said.
Earlier in the week, he met with Gulf leaders in Riyadh to try to allay fears that Washington had become less committed to their security, especially after the nuclear deal with the Saudis' regional rival Iran.
In Hanover, he will tour and speak at a massive industrial trade fair with Ms Merkel. The leaders want to breathe life into a US-European free trade accord still under negotiation which supporters say could boost each economy by some US$100 billion.
Leaders are trying to wrap up complex talks on the Transatlantic Trade and Investment Partnership (TTIP), the formal name of the accord, before Mr Obama, a Democrat, leaves office on January 20.
In Hanover, thousands of protesters holding placards with slogans like "Stop TTIP" marched on Saturday to express their opposition to the deal.