US Secretary of State Antony Blinken will discuss efforts to support Ukraine in its war against Russia, as well as the response to the conflict in the Middle East, with Prime Minister Keir Starmer and other UK officials in London on Tuesday.
In meetings with Starmer and Foreign Secretary David Lammy, Blinken will also discuss issues including the Indo-Pacific region and the AUKUS defence pact between the US, Australia and Britain, the State Department said.
The trip comes as a senior Iranian official denied reports that Tehran had supplied Russia with ballistic missiles, information a European Union spokesperson described as "credible".
CNN and the Wall Street Journal reported last week, citing unidentified sources, that Iran had transferred short-range ballistic missiles to Russia, as Moscow continues to wage war in Ukraine more than two and a half years after its 2022 invasion.
Thousands of civilians have died in the war, millions of Ukrainians have been displaced and cities and villages have become piles of rubble.
Russian forces have been slowly advancing in eastern Ukraine. A month ago, Ukrainian troops launched their first major assault on Russian territory, capturing a swath of the Kursk region.
Ukrainian President Volodymyr Zelensky has been pleading for Western nations to supply more long-range missiles and lift restrictions on using them to hit targets such as airfields inside Russia.
Blinken's visit to London also comes a week after Britain suspended some arms export licenses with Israel over equipment that could be used in the war in Gaza.
The administration of President Joe Biden and Vice President Kamala Harris, who is running to succeed him, is under pressure from critics of the war to suspend some arms deliveries to Israel, Washington's closest Middle East ally.
While Blinken is in London, he and Lammy will open talks on a UK-US Strategic Dialogue to strengthen ties which deliver growth and security, the British government said.
This will cover key elements of the UK-US relationship, including defence and security, Europe, Ukraine, the Middle East, the Indo-Pacific, and other global priorities, it added.
"In a more volatile and insecure world, it is even more important that we are highly aligned nations," Lammy said in a statement ahead of the meeting.
UK and US united over tackling Iran's influence
Lammy and Blinken, who will jointly visit Kyiv this week, said on Tuesday they are united on the need to tackle Iran's influence in the Middle East and Ukraine.
"(We are) completely aligned on the need to tackle Iran's malign activity in the region and beyond," Lammy told reporters beside Blinken, who is visiting Britain.
"We're seeing a disturbing pattern of greater Iranian support for the Kremlin's illegal group, and we discussed today our shared commitment to holding Tehran to account for their undermining of global stability."
Blinken said Iran's decision to supply Russia with ballistic missiles threatened European security and he announced further sanctions on Tehran.
Lammy said he and Blinken would travel to Kyiv this week, the first joint visit of this kind for more than a decade.