"I urge the US to avoid taking any action that would hinder other parties from continuing to make the agreement work," Johnson told parliament, adding that Britain would stay committed to the agreement as it remained "vital" to its own national security.

European leaders and key trading power China have vowed to save the accord and protect companies operating in the country following US President Donald Trump's long-expected withdrawal announcement on Tuesday.

Trump's national security advisor John Bolton said earlier that European firms doing business in Iran now have a six-month deadline to wind up investments or risk American sanctions.

"It falls to the US administration to spell out their view of the way head," said Johnson, who visited Washington earlier this week to appeal to Trump not to pull out of the nuclear deal.

"For as long as Britain abides by the agreement... then Britain will remain a party to the JCPOA (Joint Comprehensive Plan of Action," he said, adding that it would "strive to preserve the gains made by the JCPOA".

Prime Minister Theresa May earlier told parliament: "We accept that there are other issues in relation to the behaviour of Iran in the region.

"Those are issues that need to be addressed and we are working with our European and other allies to do just that," she said.