The Patriot air defense system has been described as central to protecting civilians against Russian missile attacks, but Ukraine's stockpile has run low. US President Donald Trump has said that Ukraine should be allowed to licence-manufacture the missiles, but has said on another occasion that he is "not sure."
Marco Rubio now says that talks are ongoing - but that an agreement would not solve urgent problems.
It is being negotiated right now, he says, according to Kyiv Independent, which cites Fox News.
Scaling up production, even if you have a licence, is something that takes several years because you have to build factories, says Rubio.
