President Hassan Rouhani warned on Tuesday that Iran could abandon its 2015 nuclear deal with world powers within hours if the United States keeps on imposing new sanctions.
In a speech to parliament, he also hit out at US counterpart Donald Trump saying that he had shown the world that Washington was "not a good partner".
Rouhani's comments come with the nuclear deal under mounting pressure after Tehran carried out missile tests and strikes, and Washington imposed new sanctions -- with each accusing the other of violating the spirit of the agreement.
Rouhani warned that Iran was ready to walk out of the 2015 deal, which saw the lifting of most international sanctions in return for curbs on its nuclear programme, if Washington persisted.
"Those who try to return to the language of threats and sanctions are prisoners of their past delusions," he said in the televised address.
"If they want to go back to that experience, definitely in a short time -- not weeks or months, but in the scale of hours and days -- we will return to our previous situation very much more stronger."
He said Iran did prefer to stick with the nuclear deal, which he called "a model of victory for peace and diplomacy over war and unilateralism" but that this was not the "only option".
Rouhani said Trump had shown he was an unreliable partner not just for Iran but for US allies.
"In recent months, the world has witnessed that the US, in addition to its constant and repetitive breaking of its promises in the JCPOA (nuclear deal), has ignored several other global agreements and shown its allies that the US is neither a good partner nor a reliable negotiating party," he said.
He highlighted Trump's decisions to withdraw from the Paris climate agreement and international trade deals.
Iran's parliament on Sunday approved more than half a billion dollars in funding for the country's missile programme and foreign operations of the elite Revolutionary Guards in response to the new US sanctions.
Rouhani was addressing lawmakers as deliberations start over his new ministerial line-up, which must be approved by lawmakers in the coming days.
The president, who started his second term a fortnight ago, has faced criticism from reformists over his elderly and all-male cabinet.
"I wanted to nominate three women ministers but it did not happen," he said, without explaining why.
"All ministers must use women in high-ranking positions... and especially female advisers and deputies," he added.
Rouhani, a 68-year-old moderate cleric, won a resounding re-election victory in May in large part due to the backing of reformists who supported his message of greater civil liberties and equality.
Many felt let down by the lack of women ministers, saying he had bowed to pressure from the conservative religious establishment, although he did appoint two female vice presidents and a senior aide -- positions which do not require parliamentary approval.
He defended his cabinet selections on Tuesday, and pointed to his choice for a new telecoms minister, 35-year-old Mohammad Javad Azari Jahromi, as "our first experience in choosing from the youth, someone who has grown up after the revolution".