Ukraine's president wants UN options for peace force in east Ukraine's president says a U.N.-mandated peacekeeping operation could be decisive in ending the conflict in the east with Russian-backed separatists _ and says Secretary-General Antonio Guterres should send a mission to come up with options

UNITED NATIONS -- A U.N.-mandated peacekeeping operation could be decisive in ending the conflict in Ukraine's east with Russian-backed separatists — and Secretary-General Antonio Guterres should send an assessment mission to come up with options, Ukraine's president said Wednesday.

Petro Poroshenko accused Russia of conducting an "undeclared war against my country," but said his government is ready to discuss a multinational peacekeeping operation that has "a clear objective to end the Russian aggression and restore Ukraine's sovereignty."

He told the 193-member General Assembly that it may also be time for the international community "to put Russia in its place," starting by depriving Moscow of its Security Council veto, at least on issues "related to the Russian aggression against Ukraine."

Russia's annexation of the Crimean Peninsula in early 2014 following the ouster of Ukraine's Russia-friendly president by massive protests, and its support for separatist rebels in the east, triggered a conflict with Ukrainian government forces that has claimed more than 10,000 lives and displaced 1.5 million people.

Last week, U.N. officials told the Security Council that a 2015 agreement to bring peace to Ukraine's volatile east remains largely unimplemented, and civilians are paying the highest price. The Russian and Ukrainian ambassadors blamed each other for the failure to implement the agreement, signed in the Belarus capital, Minsk.

Poroshenko said Ukraine was hopeful when Secretary-General Guterres listed resolving the Russian-Ukrainian conflict among his priorities for 2018, and expressed regret that "not much progress has been made."

He recalled that in March 2015 he asked the Security Council to deploy a U.N. peacekeeping operation in the east, but the initiative was blocked by Russia, a permanent veto-wielding council member.

Poroshenko said he was "still a strong believer" in a U.N.-mandated multinational force because it "could be a decisive factor in bringing peace to Donbas," the industrial eastern region.

"We are ready for a constructive discussion on this initiative," he said. "And a technical assessment mission which the U.N. secretary-general could send to Donbas in order to elaborate respective options would definitely assist to the discussion."

Poroshenko said, the mandate for any peacekeeping operation in the east must extend "over the entire occupied territory, including (the) border, and provide for withdrawal of Russian troops and their weaponry from our territory, as well as dissolution of all illegal bodies and structures."

Moscow has expressed readiness to discuss a possible U.N. mission, but rejected the Ukrainian demand that it should be deployed along the separatist region's border with Russia.

Poroshenko said over 87,000 Russian forces are along the Russian-Ukrainian border, and "further escalation to a full-scale war is not an unrealistic prospect" which is why full-time monitoring is needed.

Moscow has denied Ukrainian claims that it has sent regular troops to support the insurgency in the east and insists that Russian citizens fighting on the separatists' side were private citizens acting as volunteers — a point emphasized by Russia's U.N. Ambassador Vassily Nebenzia.

He also told the assembly that Poroshenko "once again turned the situation of a possible peacekeeping operation in Donbas on its head" by forgetting to say such a mission was in a proposed Security Council resolution introduced by Russia, "which did not suit Ukraine and its Western sponsors."

Nebenzia recalled that after Poroshenko's election in 2015, he "declared himself to be the president of peace, promising to immediately put an end to the conflict in Donbas." But soon after, "President Porochenko became the president of war — a war which continues to this day," the Russian ambassador said.

Addressing diplomats long after Porochenko spoke, Nebenzia said, "Today, this General Assembly hall has become nothing other for him than an election campaigning rostrum."

Porochenko is seeking a new term in the March 31 presidential election, but is trailing in opinion polls.

Nebenzia told diplomats to watch whether "today's meeting will add or not to his approval rating."

On another issue, Porochenko said he brought an appeal from thousands of Ukrainians to the U.N. chief to pressure Moscow for the release of 24 seamen detained after a Russian coast guard vessel fired on and seized three Ukrainian naval ships in the Black Sea in November.