The head of Nato said Tuesday that "Ukraine can rely on" the Western military alliance but stopped short of infuriating Russia by backing the ex-Soviet republic's membership in the Cold War-era bloc.
Nato Secretary General Jens Stoltenberg also repeated his charge from Monday that Russia was supplying pro-Moscow insurgents with weapons and troops in direct violation of a seven-month cease-fire and political reconciliation deal.
Stoltenberg completed his first visit to the war-torn country by attending a sessions of Ukraine's National Security and Defence Council - a rare honour for a foreign dignitary that underscores Kiev's desire to one day join the Alliance.
"Russia continues to support separatists forces in the east with weapons and troops. This is a violation of the territorial integrity of Ukraine," Stoltenberg told reporters after the Kiev security meeting.
"In this difficult time Ukraine can rely on Nato. Nato provides Ukraine with political and practical support."
Poroshenko's underfunded forces have been grateful for the help but still insist on shipments of offensive weapons that countries such as the United States and Britain refuse to provide.
Ukraine's 49-year-old leader - elected in the wake of last year's popular ouster of a Russian-backed president - has set for his impoverished country the goal of applying for EU membership by 2020 and later joining the 28-nation Nato bloc.
Poroshenko said Tuesday that more and more Ukrainians wanted to pull out of Russia's historic orbit and anchor their future with the West.
And he repeated his promise to one day hold a referendum on Nato that would set his government's future course.
"When, thanks to national reforms, we create all the criteria necessary for Ukraine to meet Nato membership, I will decide to hold a national referendum that will record the will of Ukraine people," Poroshenko said.
Recent polls suggest that Ukrainians back joining the Alliance's military umbrella in the face of what Kiev's leaders view as Russia's aggression in the strife-torn east.
The Kremlin denies all involvement in the 17-month conflict and calls the revolt a free expression of the mostly Russian-speaking region's will.
Europe's bloodiest conflict since the Balkans wars of the 1990s has claimed the lives of nearly 8,000 people and driven about 1.5 million from their homes.
The new Nato chief - a former Norwegian prime minister whom some have criticised for being too lenient with Moscow - stressed that the Brussels-based organisation was not trying to create a new stand-off with Russia.
"Nato doesn't seek a confrontation with Russia. Nato continues to strive for a more co-operative and constructive co-operation with Russia," he said.
"But it has to be based on some fundamental values, like respect of the borders of your neighbours."
Russia has long viewed Nato's expansion into former Soviet and Moscow-run territories of central and eastern Europe as a national security threat.
Moscow has repeatedly vowed to take unspecified reciprocal measures should Nato one day expand further east.