Donald Trump's Ukraine envoy Keith Kellogg began talks in Kyiv on Monday on security and sanctions against Russia. That's a day after the U.S. president said he would send Patriot air defence missiles to Ukraine.

The legislation, which would allow the president to levy a 500% tariff on imports from countries that purchase Russian uranium, gas and oil, has gained momentum in the Senate as Trump has signaled he will escalate US action against Russia.