President Barack Obama has warned Prime Minister Theresa May that the US will not prioritise a making a UK trade deal when the UK leaves the European Union, in favour of sealing new deals with the EU and 12 Pacific nations.

His declaration of intent to the British PM comes as May warned of "difficult times" ahead for the UK, during the G20 summit.

Obama, speaking at a joint press conference with May on Sunday (4 September) ahead of the G20 meeting in Hangzhou, assured there was still a "very special relationship" between the two nations. The outgoing US president also promised to work to stop any "adverse effects" of Brexit on the UK and the US.

The Democrat made it clear that negotiations with the EU over the controversial Transatlantic Trade and Investment Partnership (TTIP), and 12 Asia-Pacific nations around the Transpacific Partnership (TPP) would take priority.

TTIP remains in the balance after coming under scrutiny by EU ministers while the TPP – which includes Japan, Peru, Mexico, Canada and Australia – is yet to come into force after seven years of negotiations.

Obama added that it "would not make sense to put aside" existing negotiations with these big blocs of countries in order to do a quick deal with the UK.

"I've committed to Theresa that we will consult closely with her as she and her government move forward on Brexit negotiations to make sure we don't see adverse effects in our trading and commercial relationship," he told reporters.

"Obviously, there is an enormous amount of trade that already takes place… That is not going to stop. And we are going to do everything we can to make sure the consequences of the decision don't end up unravelling what is already a very strong and robust economic relationship.

"But first things first. The first task is figuring out what Brexit means with respect to Europe. And our first task is making sure we go forward on TTIP negotiations in which we have already invested a lot of time and effort."

'Difficult times ahead'

His words come as May warns of "difficult times" ahead for the UK when speaking to the BBC's Andrew Marr. May warned that the UK's abandoning of the EU would not be "plain sailing" for the UK.

"We have had some good figures and better figures than some had predicted would be the case. I'm not going to pretend that it's all going to be plain sailing," she said to the BBC. "I think we must be prepared for the fact that there may be some difficult times ahead. But what I am is optimistic."

Despite being urged by Brexiteers to invoke Article 50, to begin the two-year process of leaving the bloc, she told the show that formal EU talks will not begin until at least 2017. May also ruled out a snap election following the Brexit vote and David Cameron's resignation, saying the UK needs "stability".

May also took time in the interview to affirm her belief that voters did not want "free movement to continue in the way that it has done in the past" and that MP's were looking at "options" for new EU migration controls.

The PM said she was "very clear" that she expected the status of British citizens in other EU countries to be guaranteed and would "guarantee the status of EU citizens living here".

Theresa May
Britain's Prime Minister Theresa May (L) and U.S. President Barack Obama speak to reporters after their bilateral meeting alongside the G20 Summit, in Ming Yuan Hall at Westlake Statehouse in Hangzhou, China September 4, 2016. Reuters/Jonathan Ernst