Theresa May will tell Donald Trump an international agreement on tackling climate change should not be renegotiated when they meet for one-to-one talks as world leaders gather in Germany for the G20.
The Prime Minister has previously expressed her "disappointment" at the US president's decision to pull out of the Paris Agreement and last week joined other European leaders in voicing their continued support for the accord.
But she has previously faced criticism for failing to sign up to a statement by France, Germany and Italy that said the deal cannot be renegotiated.
A senior UK Government official said Mrs May was expected to raise climate change with the president in the talks and would stress that Britain "remains fully committed" to the agreement.
"She will say that we don't see any need for renegotiation - we support the Paris Agreement because it delivers," they said.
The PM will meet the US president on Friday on the fringes of the summit in Hamburg for talks that will also focus on growing concerns over missile testing by North Korea.
Britain condemned the launch of an intercontinental ballistic missile as a breach of United Nations Security Council resolutions that demonstrated the "grave danger" the secretive and oppressive Pyongyang regime poses to the region.
The North Korean ambassador in London was summoned to the Foreign Office for a dressing-down over the latest test.
Britain backs US calls for global action to stop the threat and Mrs May will say it is "essential" the international community is united in condemnation of North Korea's actions.
"Our focus is on working with the US and international community on how we can increase pressure and find a peaceful solution to the ongoing threat North Korea poses to international security," the official said.
"We will continue to play a central role at the UN - supporting resolutions on sanctions that will limit North Korea's ability to pursue its nuclear weapons programme.
Mrs May was the first leader through the doors of the White House after Mr Trump became president and he predicted they would have a "fantastic" relationship.
The pair were captured by photographers briefly holding hands as they walked from the Oval Office to their first press conference together.
Mrs May invited the president on a state visit to the UK but speculation that it may have been put on hold in the face of expected protests was fuelled by its absence from last month's Queen's Speech.
A surprise visit to the UK in the coming weeks, where the president could have given as little as 24 hours notice, also appeared to be on the cards but has since been ruled out by the White House.
Mr Trump is in Poland on Thursday before attending the G20. He will also attend the Bastille Day celebrations in France on July 14.