0520 GMT March 25, 2019
The United States urged Britain to drop its support for the nuclear deal and instead join the United States to counter Iran.
Writing for The Telegraph on Sunday, US Ambassador to Britain Woody Johnson said Britain should side with Washington rather than Brussels over Iran.
The US ambassador called on America's "closest ally" to reverse its position on the nuclear deal.
But senior UK government figures rejected the demands, further deepening the policy rift between the two traditional allies.
One government minister said President Donald Trump was simply throwing “red meat” to his support base and his strategy would be counterproductive, while a British foreign office source reiterated the UK's support for the agreement.
Asked about Johnson’s article, the British foreign office pointed to comments from Middle East Minister Alistair Burt, who last week ruled out Britain going along with the United States.
Burt had said that the deal was an important part of regional security and that, with the European Union, the government was trying to protect British companies from the US sanctions when dealing with Iran. However, he said Britain remained open to talks with the United States on how to address concerns about Iran.
The US envoy’s comments came just days after British Foreign Secretary Jeremy Hunt signed a joint statement with the EU which promised to push ahead with blocking the impact of the sanctions.
Despite opposition from European allies, the US president in May pulled the United States out of the deal between world powers and Tehran under which international sanctions were lifted in return for curbs on Iran’s nuclear program.
Since then, Britain, France and Germany have sought to keep the deal alive, while Trump has prepared new sanctions, saying a broader and more balanced deal is needed. Iran has denounced the sanctions as “US unilateralism”.
Johnson's comments escalate the tensions over what is the first test of the special relationship between the US and UK since Trump's successful visit to the UK last month.
Reuters and telegraph.co.uk contributed to the story.