Trump made the announcement as he met with Ukrainian President Volodymyr Zelenskyy at the Nato summit in Turkey, praising him as having "done an amazing job" and "been very effective" in the war.

"So one of the things we're going to be talking about is we're going to give a licence to you to make Patriots. That's pretty cool, right. This way, you can't complain that we're not giving them enough," Trump told Zelenskyy.

"We haven't informed the company of that yet, but that'll work out all right."

Ukraine has been struggling to shoot down Russian ballistic missile attacks as supplies of the crucial US-made Patriot interceptors run low. Zelenskyy has long sought more of the defence systems, which are expensive, in high demand and take a long time to manufacture. He's been pressing for Ukraine to be granted a license to manufacture the technology.

Despite Moscow's heavy bombardments of Kyiv in recent days, Ukraine appears to be turning the tide in the war by stabilising the front line and conducting strikes deep into Russia.

Trump said that those strikes could help to end the war.

"It's an escalation, but it's also an escalation that can help lead to an end," Trump said.

The US president repeated his belief that both Zelensky and the Russian leader Vladimir Putin want to strike a deal to halt the fighting.

"The president wants to get it done, and I believe that President Putin wants to get it done, and that should be a good combination," he said.

Though the U.S. president and his Ukrainian counterpart had a tense encounter at the White House last year, Trump said Wednesday as he sat with Zelenskyy, "We've actually developed a good relationship. It's hard to believe."

He said Ukraine has a good future with "such great land, such great assets, such great people" and that they were going to have a good talk together.

He also called Russian President Vladimir Putin a "difficult character" and Zelenskyy "a difficult character."