US Secretary of State Rex Tillerson today vowed that Donald Trump's America would be a 'steadfast ally' to Britain during Brexit.

Mr Tillerson vowed to stand shoulder to shoulder with the UK in a joint press conference with Boris Johnson at the Foreign Office.

The Secretary of State and Foreign Secretary appeared together following a day of talks on international security taking in North Korea, Iran and Libya.

The comments will renew hopes of Britain striking a quick trade deal with the US after Brexit takes place in March 2019.

US Secretary of State Rex Tillerson (pictured today at the Foreign Office) has vowed that Donald Trump's America would be a 'steadfast ally' to Britain during Brexit

Mr Tillerson vowed to stand shoulder to shoulder with the UK in a joint press conference with Boris Johnson at the Foreign Office

Mr Tillerson said: 'While Brexit does present unique challenges to the British people, please know you have a steadfast ally in the United States

'We will stand by our ally as Brexit continues to take shape. We look forward to continuing this alliance.'

Mr Tillerson earlier met Prime Minister Theresa May and the pair agreed to keep up the international pressure on North Korea at Downing Street talks today.

Britain has been a vocal supporter of tough new sanctions imposed at the United Nations Security Council after a series of North Korean nuclear tests.

Mr Tillerson visited No 10 for detailed talks with the UK National Security Adviser Mark Sedwill today before a broader meeting with Foreign Secretary Boris Johnson.

Theresa May and US Secretary of State Rex Tillerson (pictured today arriving in Downing Street) agreed to keep up the international pressure on North Korea at Downing Street talks

Mr Tillerson visited No 10 for detailed talks with the UK National Security Adviser Mark Sedwill today before a broader meeting with Foreign Secretary Boris Johnson

The US delegation swept into No 10 this morning (pictured) without a moment's pause to set our their priorities for the day's meetings

This morning's talks focused on the international threat from North Korea and Iran acquiring nuclear weapons.

After Mrs May dropped into the No 10 meeting, her spokesman told reporters: '(They) touched on the Iran nuclear deal, the PM underlining its importance in preventing Iran from procuring nuclear weapons.

'They also discussed North Korea and its continuing destabilising activities.

'They agreed on the importance of the international community continuing to work together to put pressure on the regime.'

Mr Johnson will hold joint talks with Mr Tillerson and French political director Nicolas de Riviere about the aftermath of Hurricane Irma.

The trio will also discuss fresh ways to respond to North Korea's latest nuclear test after the UN security council approved new sanctions against Pyongyang.

Foreign Secretary Boris Johnson (pictured at the Foriegn Office today) is holdinh joint talks with Mr Tillerson and French political director Nicolas de Riviere about the aftermath of Hurricane Irma

A wider meeting involving the Italian and Egyptian governments (pictured) was convened by Mr Johnson too review the latest developments in Libya

Today's meeting (pictured) is intended to try and find a way to break the political deadlock in Libya and bring stability to the North African country

The Foreign Secretary will also chair a meeting on the situation in Libya with Mr Tillerson, and the French political director, as well as the Italian and Egyptian foreign ministers, and representatives from the UN and United Arab Emirates.

The meeting is intended to try and find a way to break the political deadlock in Libya and bring stability to the North African country in a bid to help deal with the issue of illegal migration.

Speaking ahead of the meetings, the Foreign Secretary said: 'I've seen first-hand the devastation Hurricane Irma has caused people in the Caribbean. Close coordination with our allies is vital for both the short-term and long-term recovery efforts.

'Britain will continue to work closely alongside our partners to tackle the shared challenges we face worldwide.'