The United States is not seeking a regime change in Iran, US President Donald Trump said on Monday, as tensions between the two countries rise with Washington deploying troops to the region.

“I know so many people from Iran, these are great people, it has a chance to be a great country, with the same leadership,” Trump said at a press conference in Tokyo where he is on a state visit.

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“We're not looking for regime change, I just want to make that clear. We're looking for no nuclear weapons.” “I'm not looking to hurt Iran at all,” added Trump.

The US on Friday said it was deploying 1,500 additional troops to the Middle East to counter “credible threats” from Tehran, the latest step in a series of military escalations.

Tensions have been rising between Washington and Tehran since Trump's decision last year to withdraw from an international nuclear deal with Iran and reimpose sanctions on the oil producer.

The US president reiterated on Monday his criticism of that “horrible Iran deal” but said he was open to new negotiations.

“I think we'll make a deal,” he said at the press conference alongside Prime Minister Shinzo Abe.

Hours earlier, Trump had insisted, “I do believe that Iran would like to talk, and if they'd like to talk, we'd like to talk also.” Trump sounded a similarly conciliatory tone on North Korea, a key topic of his discussions in Japan, which views Pyongyang as a major threat.

The US leader, who has had two rounds of talks with North Korea's Kim Jong Un, described him as a “very smart” man who knew he needed to denuclearise.

“He knows that with nuclear... only bad can happen. He is a very smart man, he gets it well,” said Trump, who repeated that North Korea has “tremendous economic potential”.

And he once again dismissed missile launches earlier this month by Pyongyang that National Security Advisor John Bolton has said were a violation of UN resolutions. “My people think it could have been a violation... I view it as a man who perhaps wants to get attention,” Trump said.

Abe reiterated his willingness to meet with Kim himself, in particular, to raise the issue of Japanese citizens kidnapped by Pyongyang, and said Trump backed his push to hold direct talks.

In addition to North Korea, Trump and Abe have been focused on trade, with Washington and Tokyo locked in negotiations to reduce what the US president calls an “unbelievably large trade imbalance”.

Trump has said a final deal will not come until after Japan's upper house elections in July, but said he expected an agreement that would “benefit both of our economies”. He also said that Japan has “just announced its intent to purchase 105 brand new F35 stealth aircraft”.

“This purchase would give Japan the largest F35 fleet of any US ally,” Trump added.

The US president said he there was a “very good” chance of clinching a trade deal with China, despite recent retaliatory measures between the world's top economies. “I think sometime in the future, China and the US will have a great trade deal and we look forward to that,” Trump said.