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.

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