KIEV, Ukraine — Secretary of State Rex Tillerson said Sunday that Russia must make the first moves to rein in separatists and remove its weaponry from eastern Ukraine.

He also vowed that sanctions would remain in place until Moscow reverses its actions and respects the border between the two countries.

After an hourlong meeting with Ukrainian President Petro Poroshenko, Tillerson told reporters that relations between Moscow and Washington will not improve until Ukraine gets back full control of its territory from separatists he characterized as Russia’s “proxies” in two breakaway provinces.

“I have been very clear in my discussions with Russian leadership, on more than one occasion, that it is necessary for Russia to take the first steps to de-escalate the situation in the eastern part of Ukraine,” he said in a joint news conference with Poroshenko, in which he called for Russia to use its influence on the separatists to enforce a cease-fire and allow international observers to do their work safely.

Poroshenko said that during their talks, Tillerson has assured him that the United States is also committed to the return of Crimea, which Russia annexed in 2014 after a hasty election in which Russian troops were already on the peninsula.

Tillerson did not mention the word Crimea but suggested that Russia’s annexation of the peninsula remains a major sticking point, saying that “the U.S. and EU sanctions on Russia will remain in place until Moscow reverses the actions that triggered these particular sanctions.”

Tillerson was in Kiev with his new special envoy, Kurt Volker, as part of a U.S. push to resuscitate stalled negotiations over ending three years of war.

During his visit of barely three hours, Tillerson also squeezed in a meeting with young reformers who are pushing for the government to be more responsible and attractive to foreign investment. Then he left for Turkey to talk with President Recep Tayyip Erdogan about the fast-moving offensive against the Islamic State in Syria, before heading to the Persian Gulf for four days of shuttle diplomacy to mediate a dispute between Qatar and its neighbors.

The multipronged trip represents something of a pivot for the former Exxon Mobil CEO, who came to the State Department job with no diplomatic experience. After months of complaints that the department is being sidelined, Tillerson is asserting himself in a more conventional manner for the top U.S. diplomat with a round of diplomatic forays abroad.