US President Donald Trump has issued a blunt warning to countries trading with Iran after his administration this week re-imposed sanctions on the nation.

“Anyone doing business with Iran will NOT be doing business with the United States,” Mr Trump tweeted on Tuesday.

The tweet came just hours after Washington’s reimposed sanctions took effect – which he described as “the most biting sanctions ever”.

He also warned they would “ratchet up to yet another level” when tougher sanctions on oil exports begin in November.

“I am asking for WORLD PEACE, nothing less!” Mr Trump said.

The Iran sanctions have officially been cast. These are the most biting sanctions ever imposed, and in November they ratchet up to yet another level. Anyone doing business with Iran will NOT be doing business with the United States. I am asking for WORLD PEACE, nothing less!

— Donald J. Trump (@realDonaldTrump) August 7, 2018

The reimposed sanctions are being reimposed on Iran in waves after Mr Trump’s decision to withdraw from Joint Comprehensive Plan of Action, also known as the Iran nuclear deal, earlier this year.

Iranian President Hassan Rouhani said the measures were “psychological warfare” designed to “sow division among Iranians”.

He added that the US government had “turned their back on diplomacy”.

“They want to launch psychological warfare against the Iranian nation.” he said.

“Negotiations with sanctions doesn’t make sense. We are always in favour of diplomacy and talks … but talks need honesty.”

Mr Trump’s warning appears to be targeted at the European Union, which remains committed to the original nuclear agreement and has spoken out against the sanctions.

The EU has vowed in the past to protect firms doing “legitimate business” with Iran.

On Monday, the foreign ministers of Germany, France and the UK released a statement saying the nuclear deal remained “crucial” to global security.

On Tuesday, Europe launched an updated version of its “Blocking Statue” – which is intended to nullify US legal action against European firms in connection with Iran.

-with agencies