Britain's Prime Minister Theresa May has become the first foreign leader to meet US President Donald Trump since he took office a week ago.
May arrived at the White House on Friday to hold discussions on a wide range of pressing issues, including trade, at a time when the UK is in the process of quitting the European Union, or Brexit.
The two leaders were later scheduled to hold a joint press conference followed by a working lunch.
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May arrived in the United States on Thursday and received a rapturous welcome from Republican politicians gathering in Philadelphia with a speech urging them to "beware" of Russia, and warning US allies to "step up" and play a greater role in global security.
She hailed strong security ties between the two countries, and said their relationship had "defined the modern world."
"As we rediscover our confidence together, as you renew your nation just as we renew ours, we have the opportunity, indeed the responsibility, to renew the special relationship for this new age," said May, who won loud applause when she praised Trump's victory.
"It was a very careful, crafted speech, trying to set a hopeful tone for a new relationship between the two countries focusing, of course, on trade," said Al Jazeera's James Bays, reporting from the White House.
"Trying to build on what the Brits call their 'special relationship', and with the ongoing divorce from the EU trying to turn it into a special trade relationship."
Faced with exit from the European single market, the British government is scrambling to secure bilateral deals around the world.
Trump is seeking to cancel or renegotiate existing US multilateral trade agreements but has voiced interest in bilateral trade deals, specifically including Britain post-Brexit.
May also hopes to win the newly-inaugurated president's support for collective security arrangements that have underpinned European security since World War Two.
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In her speech, she suggested she saw the need for some reforms in NATO and for more countries to pay more to the alliance to help fund it, which has been Trump's main complaint about NATO.
"America's leadership role in NATO - supported by Britain - must be the central element around which the alliance is built," May said.
But she said that EU nations "must step up" to ensure NATO remains the cornerstone of the West's defence.
Trump's first week in office has been marked by a war of words with Mexico over the building of a border wall, and his vow to make Mexico pay for it.
On Thursday, Mexican Enrique Pena Nieto called off a planned trip to Washington in protest.
