His upbeat comments come with EU nations -- struggling with a migrants crisis -- hoping for signs of a de-escalation after the conflict stoked tensions in eastern Europe.
"There has not been a single shot fired," the pro-Western leader said in a televised address to students undergoing military training in Kiev.
But he added: "This is still not peace. This is not the end of the war.
"The end of war will come when every patch of Ukrainian soil is liberated from the enemy, the occupant, the aggressor. But this is not simply a ceasefire -- this is a real truce."
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The conciliatory gesture came in response to strong Western pressure for Russian President Vladimir Putin -- who denies any involvement in Ukraine's affairs -- to persuade the militias to put their vote on hold.
Poroshenko had called the planned elections "fake" and branded them another example of the rebels' refusal to commit to a truce agreed in February.
The ceasefire was often broken but has been widely upheld in the past month.
Moscow and Brussels also welcomed the rebels' announcement. Western diplomats believe the delay gives time for elections to be conducted in line with Ukrainian and international laws.
But Ukrainian Foreign Minister Pavlo Klimkin told lawmakers that no separatist polls could be held until Russia withdrew all its troops and military hardware from the war zone.
President Vladimir Putin refers to the Russian fighters captured in the rebel regions as "volunteers" and off-duty servicemen who follow "the call of their heart".
Ukrainian forces yesterday began withdrawing tanks from the demarcation line with Lugansk -- the smaller of the industrial regions resisting Kiev's leadership.