The pro-Western leader's comments were soon followed by a European Union decision to extend by another day a heated debate on unleashing new sanctions aimed at punishing Russia over what the West says is Moscow's military aggression in the ex-Soviet state.
Poroshenko said Friday's ceasefire -- the first backed by both Kiev and Moscow since the conflict erupted five months ago -- had dramatically improved security in the country's war-ravaged industrial rustbelt.
"This gives us hope that there are good prospects for he peace initiative."
Moscow denies having deployed troops or weaponry across the border, and President Vladimir Putin dismissed the NATO claims as a reckless attempt to "revive" the Cold War-era security bloc.
More From This Section
Poroshenko -- elected in May on a promise to crush the rebellion and preserve Ukraine's unity -- also waded into explosive political territory by promising to submit a bill to parliament granting parts of the east temporary self-rule.
"Ukraine will not make any concessions on issues of its territorial integrity," he said.
The Kremlin has long sought to turn Ukraine into a loose federation in which the largely Russian-speaking Donetsk and Lugansk regions establish their own trade and diplomatic relations with Moscow.
The number two in the separatist leadership of Donetsk said the vital industrial hub would seek outright independence in what promise to be arduous peace talks aimed at putting a durable end to a conflict that has frayed East-West ties.