May and Trump go head to-head at the White House

The two leaders are spending about an hour in face-to-face talks in the Oval Office, where Mr Trump has restored a bust of Winston Churchill removed by predecessor Barack Obama.

Mrs May believes Brexit and the election of Mr Trump will allow Britain and America to take up a stronger leadership role in the world.

Top of the agenda for Mrs May will be preparations for a free trade deal between the UK and US after Britain has withdrawn from the European Union.

But the pair will also discuss security challenges including Syria, Russia and the threat from Islamist terror - and Mrs May was also under pressure to challenge the president over the use of torture techniques after Mr Trump expressed support for waterboarding.

Before her meeting with Mr Trump, the Prime Minister laid a wreath at the Tomb of the Unknowns at Arlington National Cemetery.

Once inside she became the first head of government to sign the White House book under Mr Trump, his press secretary Sean Spicer said.

The president and Mrs May will hold a joint press conference - his first since his inauguration a week ago - which could highlight the differences between the two leaders despite the Prime Minister’s desire to forge a close relationship with Mr Trump.

The meeting comes as it emerged Mr Trump was expected to sign an executive action on Friday temporarily halting the flow of refugees into the US and stopping all entries from some majority-Muslim nations.

When Mr Trump first floated his plan to ban Muslims from entering the US, Mrs May said the comments were “divisive, unhelpful and wrong”.

Her meeting at the White House comes after she addressed congressmen from the president’s Republican party in Philadelphia on Thursday.

She lent her weight to Mr Trump’s call for Nato members to match the US and UK in meeting promises to spend 2% of GDP on defence.

And she offered backing for some of the president’s other foreign policy priorities, condemning Iran’s “malign influence” in the Middle East, promising to “stand up” for Israel’s security and vowing not to repeat “failed” interventions like the Blair-Bush invasion of Iraq.

But she also had words of caution for Mr Trump over his approach to Russia’s Vladimir Putin, suggesting his watchword should be “engage but beware”.

Her speech at the Republican Congressmen’s Retreat was the first time a foreign head of government had addressed the annual gathering.

In a sign of her determination to deepen links with the Republican establishment as well as the team around Mr Trump, she held private talks with senior congressmen including House of Representatives speaker Paul Ryan and Senate majority leader Mitch McConnell.

Aides said the meeting with Mr Ryan focused on trade and he told Mrs May that Republicans in both houses were very keen to work with the UK on a deal beneficial for both sides.

Following their press conference in the East Room of the White House, the two premiers will continue their talks over a working lunch in the State Dining Room.