The decision is part of a larger reshuffle of the Ukrainian government. Klymenko had previously been mentioned as a possible replacement in the post of defense minister, after Mykhailo Fedorov was forced to resign after just six months in office. Fedorov's dismissal led to protests around the country.
Klymenko replaces Rustem Umyrov, who has been secretary of the National Security and Defense Council for the past year. He also heads Ukraine's delegation in peace talks with the United States and Russia, which have been stalled since February.
