Boris Johnson has held a call with US President Joe Biden and other world leaders after returning from his second holiday of the summer.
The Prime Minister discussed the Russian-occupied nuclear complex in Ukraine with the US president, France’s Emmanuel Macron and German Chancellor Olaf Scholz on Sunday.
Downing Street said he had returned to the UK and is expected to fully resume work in No 10 again from Monday.
He had been holidaying with wife Carrie Johnson in Greece after their honeymoon to Slovenia.
The leaders discussed co-operation on international security, including the risk of the fighting around the Zaporizhzhia nuclear plant occupied by Vladimir Putin’s troops.
They welcomed the Russian president’s agreement to allow the UN’s International Atomic Energy Agency (IAEA) to visit the site amid concerns over its safety.
“They stressed the importance of ensuring the safety and security of nuclear installations and welcomed recent discussions on enabling an IAEA mission to the Zaporizhzhia facility,” a No 10 statement said.
The men also discussed efforts to prevent nuclear proliferation in Iran.
“The Prime Minister welcomed the opportunity to speak, and the leaders agreed their teams would continue working closely together in the coming weeks,” No 10 added.
Johnson had faced criticism for being on holiday as the UK’s economic picture worsened, with inflation soaring and energy prices set to shoot up again.
Asda chairman and Tory peer Lord Rose criticised a “horrifying” absence of fresh support, and said: “The captain of the ship is on shore leave – nobody is in charge at the moment.”
Deputy Labour leader Angela Rayner said Johnson had “abdicated his responsibility and bailed on the country” in his final weeks in No 10 ahead of his replacement, either Liz Truss or Rishi Sunak, taking over on September 6.