The president laid out a military strategy to respond to the pro-Russian armed separatist unrest in Ukraine's eastern region.
"We will be attacking and liberating our land. The end of the ceasefire is our response to terrorists, rebels, looters, all those who mock the civilians, who paralyze the economy of the region, who sabotage the payment of salaries, pensions, educational allowances, who blast railroads, destroy water pipes, those who have already deprived people of a normal peaceful life."
Poroshenko's decision to respond militarily suggests he distrusted Russian President Vladimir Putin's assertions that Moscow was supportive of the ceasefire.
Military action also flies in the face of a joint request made by Putin, French President Francois Hollande, and German Chancellor Angela Merkel on Sunday for Poroshenko to further extend his declared "unilateral ceasefire."
The Ukrainian military, Poroshenko announced Tuesday, will now go on the offensive.
"The Armed Forces, the National Guard, the State Border Service, the Security Service have been given corresponding orders. The implementation of the tasks set today to defend the territorial integrity is no longer limited by the ceasefire."
He urged "every resident in Donetsk and Luhansk regions ... to become an ally for restoring security in Donbas," and appealed to armed militants to lay down their weapons with the promise that those who did so would not face prosecution.
"Disarmament and decentralization, the free use of the Russian language, the rebuilding of lost housing at the expense of the state and a joint program with the European Union for the creation of new jobs, and even the ceasefire -- all these issues we're ready to return to at any moment when we see that all parties start to observe the implementation of the major clauses of the peace plan."
The president explained that he could no longer extend the ceasefire because "Separatists' political leaders have demonstrated unwillingness and inability to control their terrorist units and gangs of looters." The militants, he noted, had committed over 100 violations during the 10-day ceasefire.