US Ambassador to the UK Woody Johnson asked Britain to support US President Donald Trump's stance on Iran, the Telegraph reported.
Otherwise, Johnson said, UK businesses would face "serious trade consequences."
In an op-ed for the Telegraph, Johnson wrote, "America is turning up the pressure and we want the UK by our side. It is time to move on from the flawed 2015 deal."
"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.
"The President has been explicit: any businesses which put their own commercial interests in Iran ahead of the global good will risk serious consequences for their trade with the United States.
"Only by presenting a united front can we exert the maximum possible pressure on the Iranian regime and get them to finally change course and put an end to their malign and reckless activities both at home and abroad."
Johnson also noted that the 2015 nuclear deal caused Iran to become "bolder" and did "not diminish" the dangers the country presents to the international community.
The Telegraph noted that UK officials have rejected Johnson's request.
Last week, the European Union (EU) issued a "blocking statute" Monday to protect European businesses from the impact of the sanctions.
The EU has been working to save the nuclear deal after US President Donald Trump pulled out of the 2015 deal in May. Last week, Trump signed an executive orderofficially reinstating US sanctions against Iran.
The sanctions target Iran's access to American dollars and steel and automobile industries, ban trade with Iran in gold and other precious metals, and include other sanctions which were lifted under the 2015 deal.
Additional sanctions will be imposed on November 4, targeting Iran's oil and shipping industries.