President Donald Trump is downplaying the possibility of sending Ukraine long-range weapons as Kyiv awaits an injection of U.S. weaponry that it hopes will help it beat back an intensifying Russian air offensive.

A Russian official says American Daniel Martindale has been rewarded with citizenship for spying on Ukraine, "by decree of our President Vladimir Putin."

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.

Ukraine's security agency says it has killed Russian agents suspected of assassinating a senior officer in Kyiv.