The US/Iran nuclear agreement was hailed as one of Barack Obama’s biggest successes leading to an improved relationship between the two countries.
However in recent months relations have deteriorated as Trump has become increasingly critical of Iran.
In an article for the Sunday Telegraph, Robert Wood Johnson said the Iranian regime is “squandering its money on proxy wars and malign activities abroad”.
Over the past few days, new protests have broken out across the country including in Tehran, the capital city.
Ambassador Johnson linked the protests to the rising unemployment and “rampant inflation” meaning many Iranians are finding it harder to survive.
He also critiqued the regime for “lining its own pockets at the people’s expense”.
Mr Johnson added the “Iranian people deserve better. They deserve a government that cares more about improving their lives than destroying others”.
Iran has been accused of unsettling peace in the region by backing President Assad of Syria.
Calling Britain the “closest ally” of the US, Ambassador Johnson urged Britain and America to work together to create a new agreement.
Mr Johnson believes that if the US and Britain present a united front then more pressure can be applied to the Iranian regime.
He said: “We are asking global Britain to use its considerable diplomatic power and influence and join us as we lead a concerted global effort towards a genuinely comprehensive agreement. Together, we can help bring about the peace and prosperity in Iran that the whole world wants to see.”
His comments come after the first phase on new sanctions the US were imposed on Iran on the 7th August.
These included limits on the automation industry as well as gold and precious metals.
A second phase of sanctions are due to be introduced on 7th November which will include Iran’s oil exports.
Mr Johnson has said America wants the UK supporting them as they aim to force Iran to change the way the country is run.
However, he said the US will not resume commercial and diplomatic relations until “tangible and sustained changes” are made so that Iran behaves like a “normal country”.