By Humeyra Pamuk and Jasper Ward WASHINGTON, April 28 (Reuters) - The acting U.S. ambassador to Kyiv Julie Davis will step down from her post and retire, a U.S. official and the State Department said on Tuesday,

You cannot threaten the free world and lead it at the same time. No nation can match American might, but for the first time in my adult life, the moral and strategic heart of the defense of liberal democracy doesn’t beat in Washington.

Ukraine has developed cutting-edge and battle-tested drone technology that has proved essential in holding back Russia’s bigger army and has drawn military interest from around the world.

President Volodymyr Zelenskiy has leveraged Ukraine's expertise in drone warfare into a series of successful diplomatic deals during visits to the Middle East and Europe, showcasing how Kyiv is using military prowess to ​boost its diplomatic clout.

Soldiers are training for drone-on-drone combat using Bumblebee drones, which have been used in Ukraine and are being sent to U.S. training centers in the Middle East.

Former Senate Republican Leader Mitch McConnell (Ky.), who now chairs the powerful Senate Defense Appropriations Subcommittee, is taking the Pentagon to task for sitting on $400 million in military aid to Ukraine authorized by Congress.

The U.S. ambassador to Ukraine will leave her post this June, after spending barely a year in the role.

I’m absolutely proud of representing the nation of free, brave, and the most stoic people, I think, on the whole planet,” Stefanishyna told me, as Russia continued to slam Ukrainian cities with drones and ballistic and cruise missiles.