US President Donald Trump on Tuesday signed a directive restoring the so-called maximum pressure policy on Iran of his first term and warned of "catastrophic" consequences if Tehran does not make a deal on its nuclear program.

Trump said he hoped for an agreement denying Iran nuclear weapons "so that it doesn't end up in a very catastrophic situation," but sounded a dovish note by saying he was prepared to speak with his Iranian counterpart.

"I really want to see peace, and I hope that we're able to do that. They cannot have a nuclear weapon," he told reporters at a press conference alongside Israeli Prime Minister Benjamin Netanyahu in the White House.

"It's very simple. I'm not putting restrictions. They cannot have one thing. They cannot have a nuclear weapon," Trump said.

Iran has denied seeking a nuclear weapon, but Israel has long contended Tehran wants a bomb and that its arch-enemy poses an existential threat.

In withdrawing the United States from a 2015 international nuclear deal in his first term, the Trump administration cited not only its alleged inability to curb Iran's quest for a bomb but also the deal's failure to address Iran's missile program or support for armed allies in the region.

Trump added that if he believed Iran was going to possess a nuclear bomb, that would be "very unfortunate" for Tehran.

"If, on the other hand, they can convince us that they won't, and I hope they can ... it's actually very easy to do, I think they're going to have an unbelievable future."

Iran Directive

Trump earlier in the day signed a directive reviving the maximum pressure policy aimed at driving the Islamic Republic's oil exports to zero.

"This is one that I'm torn about," Trump told reporters in the Oval Office. "Everybody wants me sign it. I'll do that. It's very tough on Iran," he said.

Asked if he would engage in conversations with his Iranian counterpart, Trump responded, "I would." It was not clear whom he meant.

Iran was "too close" to being able to acquire a bomb, Trump added, saying the US has the right to block Iran's oil sales to other nations and threatened Iran with "total obliteration" should they seek to kill him in retaliation.

US law enforcement last year accused Iran of seeking Trump's assassination as retaliation for his order to kill top Iranian commander Qassem Soleimani in 2020.

Trump said he hoped he would not have to follow through on the memorandum.

"Hopefully we're not going to have to use it very much. We will see whether or not we can arrange or work out a deal with Iran and everybody can live together."

Speaking before his White House meeting with Netanyahu, Trump said his predecessor Joe Biden allowed Iran to grow stronger and richer.

"They're not weak. They're very strong right now," he said.

Netanyahu praised Trump for the renewed pressure on Iran, his original decision to pull out of the nuclear deal and helping midwife a Gaza ceasefire deal freeing some Israeli hostages.

Israeli military blows over the course of a 15-month war with Iran and its armed allies, he told the news conference, had weakened the Islamic Republic.

"Israel has never been stronger and the Iran terror axis has never been weaker," he said.

'Malign influence,' snapback

The directive instructs the US Treasury to enforce sanctions and compliance measures against entities that breach current restrictions, Reuters reported earlier on Tuesday citing a US official.

Trump's policy on Iran will be aimed at denying Washington's Mideast nemesis all paths to a nuclear weapon and countering Iran's "malign influence," the official was quoted as saying.

Secretary of State Marco Rubio will also adjust or retract sanctions waivers, working with the Treasury to reduce Iranian oil exports to zero, the official added.

The US ambassador to the United Nations will work with allies to "complete the snapback of international sanctions and restrictions on Iran," the official said.

Snapback refers to the restoration of UN sanctions on Iran which were lifted by a 2015 international deal over Iran's nuclear program, which would likely need to be activated by European parties to the agreement after the US withdrew in 2018.

Trump's maximum pressure approach in his first term beginning in 2018 pummeled Iran's economy, causing a dramatic decline in oil exports and skyrocketing inflation.

In response, Tehran began to taper its adherence to the nuclear deal and ramped up military involvement in the region. During his first term, Trump also ordered the assassination of top Iranian commander Qassem Soleimani in a drone strike in 2020, depriving Iran of its wiliest military operator in the region.

Israeli Prime Minister Benjamin Netanyahu is due to meet Trump in Washington on Tuesday, and their strategy on Iran and its nuclear program is due to loom large.

Over 15 months of punishing military blows by Israel against Iran and its armed Mideast allies has weakened the so-called Axis of Resistance Tehran leads.

Trump said last month that he hoped a deal over Iran's nuclear program would mean the United States did not have to support an Israeli attack on Iran.

Long opposed to foreign wars, Trump has nevertheless adopted a hard line on Iran, saying that Iran cannot be allowed to have a nuclear weapon but also maintaining that Washington should not pursue regime change.