US Secretary of State Marco Rubio says negotiations with Ukraine on a potential agreement to end the Russia-Ukraine war were productive, though “more work remains.” The talks took place in Florida with a Ukrainian delegation led by national security council secretary Rustem Umerov, the country’s new chief negotiator. US Secretary of State Marco Rubio says negotiations with Ukraine on a potential agreement to end the Russia-Ukraine war were productive, though “more work remains.” The talks took place in Florida with a Ukrainian delegation led by national security council secretary Rustem Umerov, the country’s new chief negotiator.