Boris Johnson has spoken on the phone to US President Donald Trump, as his recovery from coronavirus continues.
The prime minister, who is recuperating at his official country residence, is also expected to speak to the Queen by phone this week.
Downing Street said Mr Johnson is currently not doing any formal government work but is receiving updates from senior colleagues.
No 10 said he had thanked Mr Trump for his good wishes whilst he was unwell.
A spokesperson added the pair had discussed UK-US cooperation in the fight against the virus, and agreed on the importance of a "coordinated international response".
Earlier No 10 said Mr Johnson has spoken to Foreign Secretary Dominic Raab, who has been deputising for him for the past two weeks, and "senior members of his team".
Downing Street also said Mr Johnson - who spent nearly a week in hospital and three nights in intensive care - was "continuing his recovery" at Chequers, his country retreat in Buckinghamshire.
After he was discharged from hospital on 12 April, Mr Johnson - who received oxygen treatment to help his breathing during his stay - praised NHS staff, saying it "could have gone either way".
His fiancée Carrie Symonds, who is expecting their first child, said she had been through some "very dark times".
The prime minister is not performing any official engagements at the moment and Mr Raab is expected to stand in for him at Prime Minister's Questions on Wednesday - the first since the Easter recess.
The PM last chaired the government's daily virus briefing on 26 March, testing positive for the virus later that evening.
The PM's anticipated phone conversation with the Queen would be the first for three weeks, No 10 said. Their traditional weekly face-to-face meeting has not taken place since early last month.
The Queen, who celebrated her 94th birthday on Tuesday, is currently in residence at Windsor Castle, having moved there from Buckingham Palace in the middle of March.