U.S. and Ukrainian officials completed roughly four hours of talks Sunday aimed at finding an endgame to the war between Russia and Ukraine.

Secretary of State Marco Rubio told reporters afterward that the session was productive, but work remains in the search for a peace deal.

“It’s not just about ending the war,” Rubio said. “It is about securing Ukraine’s future, a future that we hope will be more prosperous than it’s ever been.”

The head of Ukraine's security council, Rustem Umerov, made comments that underscored Ukraine’s gratitude for U.S. support during nearly 4-year long war. But the Ukrainian official offered no hints about what, if any, progress was made during the talks.