British Foreign Secretary Boris Johnson is travelling to the United States on Sunday for a two-day visit, during which he will meet Vice President Mike Pence and national security adviser John Bolton, Britain said.
The discussions in Washington will centre on Iran, North Korea, Syria and other issues, according to Britain's foreign ministry, and come ahead of a visit to Britain by President Donald Trump planned for July 13.
"On so many of the world's foreign policy challenges the UK and US are in lockstep," Johnson said in a statement, citing the poisoning in Britain of Russian double-agent Sergei Skripal, and opposition to the use of chemical weapons in Syria and to the development of nuclear weapons in North Korea.
"The UK, US, and European partners are also united in our effort to tackle the kind of Iranian behaviour that makes the Middle East region less secure - its cyber activities, its support for groups like Hezbollah, and its dangerous missile programme, which is arming Houthi militias in Yemen," he added.
Trump has said he wants to reimpose US sanctions on Iran that were lifted in 2015 in exchange for Iranian commitments to curb its nuclear programme.
He has given Britain, France and Germany - who still back the deal - a May 12 deadline to fix what he views as its flaws.
These include its failure to address Iran's ballistic missile programme, the terms by which inspectors visit suspect Iranian sites, and "sunset" clauses under which some terms expire.
Trump also caused upset in Britain and France on Saturday by suggesting US-style gun rights might have stopped a recent surge in knife crime in London and past deaths from terrorist attacks in Paris.