US President Donald Trump has signed an executive order reimposing sanctions on Iran, three months after pulling out of the Iran nuclear deal.

Mr Trump said the US policy is to levy “maximum economic pressure” on the country. In a statement on Monday, the US President restated his opinion that the 2015 international accord to freeze Iran’s nuclear program in return for lifting sanctions was a “horrible, one-sided deal”.

He said it left the Iranian government flush with cash to use to fuel conflict in the Middle East.

US President Donald Trump has signed an executive order reimposing sanctions on Iran, three months after pulling out of the Iran nuclear deal. Picture: Getty Images/AFP

He said the US is urging all nations “to make clear that the Iranian regime faces a choice: either change its threatening, destabilising behaviour and reintegrate with the global economy, or continue down a path of economic isolation”.

“I remain open to reaching a more comprehensive deal that addresses the full range of the regime’s malign activities, including its ballistic missile program and its support for terrorism,” Mr Trump said in a statement.

Mr Trump warned that those that don’t wind down their ties to the Iranian economy “risk severe consequences” under the reimposed sanctions.

It comes as a senior Trump administration official said the United States is “not particularly concerned” by EU efforts to protect European firms from the reimposition of sanctions on the country.

The official was not authorised to discuss the matter by name and spoke to AP on Monday on condition of anonymity.

The European Union issued a “blocking statute” on Monday to protect European businesses from the impact of US sanctions set to return on Monday at midnight (2pm AEST).

The official said the US will use the sanctions aggressively and cited Iran’s severe economic downturn this year as evidence the sanctions would prove to be effective despite opposition from the EU, China and Russia.

Mr Trump warned that those that don’t wind down their ties to the Iranian economy “risk severe consequences” under the reimposed sanctions.

eanwhile, European foreign ministers said they “deeply regret” Mr Trump’s decision.

A statement on Monday by European Union foreign policy chief Federica Mogherini and foreign ministers of France, Germany and the United Kingdom insisted that the 2015 Iran nuclear deal “is working and delivering on its goal” of limiting Iran’s nuclear program.

UN inspectors said Iran was complying with the deal, but Mr Trump argued that it didn’t do enough. But the European ministers said the Iran deal is “crucial for the security of Europe, the region and the entire world”.