Washington DC - The US is negotiating with Ukraine over licenses to produce Patriot interceptors that would help fend off Russian missile attacks, US Secretary of State Marco Rubio said in an interview broadcast Wednesday.

But granting licenses for manufacturing the air defense systems was not "an immediate solution" given that it takes "multiple years to build these factories," Rubio said.

"I mean, these are highly sophisticated weaponry," he said on Brian Kilmeade's radio show on Fox News.

Asked if he was against granting Ukraine the Patriot licenses, Rubio said: "That's being negotiated now. That may come to fruition, but it really won't solve the short-term challenge that they're pointing to."

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During a July visit to Washington, Ukrainian President Volodymyr Zelensky said he had discussed obtaining licenses for making Patriot interceptors with his counterpart, Donald Trump.

At the time, Trump said the US should be "very careful" before granting Ukraine authorization.

Both Kyiv and Moscow have intensified airstrikes on each other in recent months, inflicting a growing number of civilian casualties, more than four years after Russia's invasion of Ukraine in February 2022.

Defense against ballistic missiles, which are particularly difficult to intercept, is a top priority for Kyiv.

"The whole world is asking for more air interceptors," Rubio said in the interview.

"It's become the number one defense need on the planet, not just for Ukraine, but on the planet," including in the Middle East because of the US-Israeli war against Iran.

"It's just a question of availability," he said. "And obviously, I have to remind people the United States has needs.

"We have our own defense needs; we have our own defense requirements," he continued. "And before we can help others, we have to make sure that our stockpiles are always sufficient."

The issue of weapons, ammunition, and interceptor supplies has become particularly acute since the start of the Iran war.