The prospects for a peacekeeping mission in Ukraine were not immediately clear. Any UN Security Council mandate would be subject to a possible Russian veto.
Poroshenko said he hoped for a European Union police mission. Any EU-only plan appeared likely to be rejected by Russia, which has said it views Nato's encroachment on its borders as a security threat.
"I invite you to discuss an invitation to a UN peacekeeping mission," Poroshenko told his top security advisers, according to Ukrainian news outlets.
The US has suspended the decision on whether to send heavy weapons to Ukraine while waiting to see whether an agreement signed last week in Minsk would lead to an end to the violence, the American envoy to Nato has disclosed.
Senior figures in the Administration, led by Vice-President Joe Biden, have been accusing Kremlin-backed separatists of breaking the accord as they continued to attack and eventually captured Debaltseve.
The White House warned that continued violations will mean "that costs to Russia will rise".
However, ambassador Douglas Lute said during a visit to London that while the debate on arming the Kiev Government continues in Washington, no decision on the issue is likely to take place "in the immediate future".
A number of America's Western allies, most notably Germany and France, are adamantly opposed to arms being sent to Ukraine, maintaining it will set back the chances of achieving peace.
Lute stressed that President Barack Obama fully understood the case put forward by Chancellor Angela Merkel that the strength of the Western alliance over Ukraine lay in a stance based on "solidarity and cohesion".
"Mr Putin is trying drive a wedge in that solidarity, whether it's between Nato and the US, between EU member states on sanctions. Those who are advocating immediate arming [of Ukraine] need to take that into account," he said.
Lute, a former army Lieutenant-General, has served in the White House under Presidents George W Bush and Obama and is said to have influence in Washington. He refused to comment on his personal views on arming the Ukrainian forces, pointing out that the decision is not up to him.
However, he added: "I am a cohesion kind of guy."
Lute said the large numbers of Russian troops and armour, which Nato and the US accused Moscow of sending into Ukraine, has now gone back across the border.
What is left, according to American assessment, are separate teams totalling "several hundred" personnel including special forces, communications and electronic warfare specialists, intelligence officers and a parallel command and control structure to the separatist forces answerable directly to Moscow.
The advanced systems in use on the frontline have been manned by Russian forces. Their effective use "does not happen by giving these to a bunch of thugs", said Lute. "In our experience with the US forces it takes 10, 12 years of professional training to do this."
However, senior diplomatic sources hold that the Kiev Government has been reconciled to losing Debaltseve, and having achieved their objective, the rebels are unlikely to continue their offensive for much longer.
- Washington Post-Bloomberg, Independent
