But Western powers fear that President Vladimir Putin is seeking to limit the force's mandate in such a way that any ceasefire would simply consolidate his allies' gains.
Tillerson is due in Vienna on Thursday for talks with the Organization for Security and Cooperation in Europe and U.S. officials say he is expected to meet Lavrov there. "In France, journalists from the Sputnik news agency are denied access to news conferences, the United States authorities impose major restrictions on the activity of RT television, labeling it as a foreign agent", he went on to say.
But Russian Foreign Minister Sergei Lavrov, in a long and grievance-filled speech to the OSCE, said an expanded mandate would be akin to an occupation.
"We prioritise ending the violence, that's our first priority, and to seek to do that we need to put a peacekeeping force in place", Tillerson said.
"Russia is arming, leading, training and fighting alongside anti-government forces".
"And we've made this clear to Russian Federation from the very beginning, that we must address Ukraine", he said.
"We call on Russian Federation and its proxies to end the harassment, intimidation and its attacks on the OSCE special monitoring mission", he added.
He and Lavrov met on the sidelines of the conference, though both ignored reporters' questions when the meeting began.
"We should be clear about the source of this violence", Tillerson said.
In his speech, he referred to the 2015 Minsk ceasefire agreement, brokered in the Belarussian capital by France, Germany, Russia and Ukraine.
Economic sanctions were placed on Russian Federation by then-US President Barack Obama in 2014 following the country's military action in Crimea and Ukraine.
Russia's foreign minister called on Organization for Security and Cooperation in Europe (OSCE) countries to strengthen efforts to ensure the safety of the internet on Thursday.
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