US President Donald Trump has said that America will impose major additional sanctions on Iran in a bid to prevent the country obtaining nuclear weapons.

In a tweet, Trump said the major additional sanctions will come into force on Monday. He said economic pressure will be maintained unless the leadership in Tehran changed course.

It comes after Iran announced it will exceed internationally agreed limits on its nuclear programme. The limit on its stockpile of enriched uranium was set under a 2015 nuclear deal with world powers.

In return, relevant sanctions were lifted, allowing Iran to resume oil exports – the government’s main source of revenue. But the US pulled out of the deal last year and reinstated sanctions.

This triggered an economic meltdown in Iran, pushing the value of its currency to record lows and driving away foreign investors. Iran has responded by scaling back its commitments under the nuclear deal.