Donald Trump's top trade official last night warned Britain will have to wait to strike a post-Brexit trade deal with the United States.

Robert Lighthizer said it is 'too early to have a negotiation' because the UK is still a member of the Brussels club.

His comments are a blow for the Government and strike a very different tone to Mr Trump's earlier pledge to strike a Brexit trade deal 'very very quickly'.

And they emerged hours after Theresa May and Canadian Prime Minister Justin Trudeau announced they had agreed to strike a 'swift' trade deal after we leave the EU.

The pair said they would use the existing EU-Canada trade agreement, known as Ceta, as a blueprint for a 'seamless' transition to the UK's own deal.

It comes as Mrs May and the US President are expected to meet as the two leaders are both in New York at the UN General Assembly.

US trade representative ambassador Robert Lighthizer shake hands with British international trade secretary Liam Fox in the US earlier this year. Mr Lighthizer has now said the UK will have to wait for a post-Brexit trade deal with the US, warning it is 'too early' for negotiation

Speaking at an event in Washington yesterday, Mr Lighthizer outlined the US position on Brexit to an audience at the Center for Strategic and International Studies.

In comments reported in The Times, he said: 'Even when it's going to happen is not quite clear yet . . . But we have had meetings. It's too early to have a negotiation.

'They don't really have competence in that area, but it's something that's on the horizon.'

Britain cannot strike free trade deals before it has left the EU because we are still bound by the commons tariffs decided in Brussels.

But the UK has stepped up efforts to try to lay the groundwork for a series of trade deals which the UK can seamlessly strike when we quit the bloc in March 2019.

Theresa May, pictured last night with Canadian PM Justin Trudeau as the pair watched a wheelchair basketball match. She is on a global charm offensive to drum up support for post Brexit trade deals, and yesterday the pair agreed to plans for a 'swift' transition to a deal

Mrs May has been on a charm offensive to countries including Japan and Canadato drum up support for post-Brexit trade deals.

And earlier this year Liam Fox, the international trade secretary, visited Washington to hold talks with Mr Lihthizer to discuss hopes for a trade deal.

A statement put out by the US state department following the meeting in July said the pair 'committed to strengthen economic links between the UK and US, including a discussion about the possibility of laying the groundwork for a potential new trade agreement soon after Brexit'.

Speaking at the visit, Dr Fox said: ''As our largest single trading partner, we have a strong foundation to build on as we start preparation on joint work to explore a future ambitious trade agreement once the UK has left the EU.'

While Mr Lighthizer said the UK is an 'invaluable trading partner' and said he looked forward to working with Britain to 'lay the groundwork for our future trade relationship, including exploring the possibility of a new US-UK trade agreement.