Hassan Rouhani also said the country could quickly bring the nuclear programme to even more advanced levels than when Iran reached a deal with world powers that limited its ability to produce nuclear weapons.

His remarks to politicians follow the Iranian parliament's move earlier this week to increase spending on the country's ballistic missile programme and the foreign operations of its paramilitary Revolutionary Guard.

The bill - and Mr Rouhani's comments - are seen as a direct response to new US legislation earlier this month that imposed mandatory penalties on people involved in Iran's ballistic missile programme and anyone who does business with them.

The US legislation also applies terrorism sanctions to the Revolutionary Guard and enforces an existing arms embargo.

If Washington continues with "threats and sanctions" against Iran, Mr Rouhani said in parliament on Tuesday, Tehran could easily restart the nuclear programme.

"In an hour and a day, Iran could return to a more advanced (nuclear) level than at the beginning of the negotiations" that preceded the 2015 deal, Mr Rouhani said.

The landmark agreement between Iran and world powers two years ago capped Iran's uranium enrichment levels in return for the lifting of international sanctions.

The US and other world powers fear Iran sought the ability to produce atomic weapons. Iran has long denied that it seeks nuclear arms and says its nuclear programme is only for peaceful purposes.

It was not immediately clear what Mr Rouhani was referring to - and whether he meant Iran could restart centrifuges enriching uranium to higher and more dangerous levels.

He also offered no evidence of Iran's capability to rapidly restart higher enrichment, though Iran still has its stock of centrifuges.

Those devices now churn out uranium to low levels that can range from use as reactor fuel and for medical and research purposes, but could produce the much higher levels needed for a nuclear weapon.

However, in December Mr Rouhani ordered plans on building nuclear-powered ships, something that appears to be allowed under the nuclear deal.

Mr Rouhani's remarks were likely an attempt to appease hardliners at home who have demanded a tougher stand against the United States.

But they are also expected to ratchet up tensions further with the Trump administration.

Iran has said the new US sanctions amount to a "hostile" breach of the 2015 nuclear deal.

"The US has shown that it is neither a good partner nor a trustable negotiator," Mr Rouhani added. "Those who are trying to go back to the language of threats and sanctions are prisoners of their past hallucinations. They deprive themselves of the advantages of peace."

But Mr Rouhani also tempered his own threat, adding that Iran seeks to remain loyal to its commitments under the nuclear deal, which opened a "path of cooperation and confidence-building" with the world.

"The deal was a model of the victory of peace and diplomacy over war and unilateralism," said Mr Rouhani. "It was Iran's preference, but it was not and will not remain Iran's only option."