US Secretary of State Rubio said the trilateral Ukraine-US-Russia talks held in Abu Dhabi were "very productive", but "a lot of work" needs to be done to achieve peace.
"Our goal is to expand the tripartite format so that not only the US, Ukraine and Russia are represented at the negotiating table, but also Europeans," he said.
He was also asked whether the Russian negotiators who arrived in Abu Dhabi are serious about ending the war.
"That's what we're checking," the official replied.