Boris Johnson has spoken to US President Donald Trump ahead of meeting him on Sunday for the first time since becoming prime minister.
The leaders, who will meet at the G7 summit in France, discussed “foreign policy issues and global trade” in a phone call on Friday evening.
No 10 said they “looked forward to speaking further” at the summit.
Mr Trump has consistently praised Mr Johnson, and predicted a speedy US-UK trade deal after Brexit.
The UK wants protections for the NHS and animal welfare standards in any future deal, but also wants it to cover issues such as opening up agricultural markets, services and public procurement.
Senior Trump administration officials are “very enthusiastic” about the prospect of a trade deal – or a series of mini agreements – and want to make progress quickly.
But the British side is adamant it wants to secure the right deal rather than a quick agreement, even though it is seen as a major post-Brexit prize.
A UK government spokesman said: “Of course we want to move quickly, but we want to get the right deal that works for both sides.”
The prime minister will meet Mr Trump for one-on-one talks on the sidelines of the summit on Sunday morning.
The G7 meeting in Biarritz – a get together of most of the leaders of the world’s largest economies – comes with just over two months until the UK is scheduled to leave the European Union on 31 October.
Mr Johnson will meet European Council President Donald Tusk on Sunday in their first face-to-face meeting and spell out his absolute commitment to getting the UK out of the EU on that date.
Ahead of his first summit as prime minister, he insisted the UK would be an “energetic partner” on the world stage after Brexit.
Mr Johnson said: “Some people question the democratic decision this country has made, fearing that we will retreat from the world. Some think Britain’s best days are behind us.
“To those people I say: you are gravely mistaken.”
His comments come after French President Emmanuel Macron suggested a post-Brexit trade deal with the US could see Britain as a “junior partner” in a position of “historic vassalisation”.
The G7 summit follows a hectic week of diplomacy for Mr Johnson, who visited Paris and Berlin in an effort to persuade the EU to amend the withdrawal agreement it reached with his predecessor Theresa May.
The prime minister wants to renegotiate the Irish backstop – a key Brexit sticking point which is part of the agreement and aims to prevent a hard border on the island of Ireland after Brexit. The EU has consistently ruled this out.
If implemented, the backstop would see Northern Ireland staying aligned to some rules of the EU single market, should the UK and the EU not agree a trade deal after Brexit.
Mr Johnson previously said that would mean “signing away” the UK’s “economic independence”.
At a news conference on Wednesday with Mr Johnson, German Chancellor Angela Merkel suggested an alternative to the backstop might be achievable, adding that the onus was on the UK to find a workable plan.
But the next day Mr Macron indicated the issue was not up for renegotiation, saying it was “indispensable” to preserving political stability and the single market.
After visiting his counterparts Mr Johnson reported “new mood music”, but said said reaching a new deal would not be “a cinch”.
He has insisted the UK will leave the EU by the end of October, whether or not a new deal is reached.
The G7 summit, which also comprises Canada, France, Germany, Italy, Japan and the United States, runs from Saturday to Monday.
Issues on the agenda include the global economy, tackling inequality and responding to the challenges of the digital age and the rise of artificial intelligence.
On Friday, Mr Macron – who is hosting the summit – and Mrs Merkel said the ongoing fires in Brazil’s Amazon rainforest must be discussed among the G7 leaders this weekend.