Speaking to thousands of supporters on January 29, the confectionary magnate said that a "feeling of deep responsibility before the country and…before past and future generations" led him to decide to run for a second five-year term in the March 31 vote.
The 53-year-old Poroshenko, one of Ukraine's richest men, came to power in the aftermath of the pro-European Maidan protests that pushed Moscow-friendly President Viktor Yanukovych out in February 2014.
He has vocally advocated closer integration with the West and criticized Russia following Moscow's seizure of Ukraine's Crimea region and amid a continuing war against Russia-backed separatists in the eastern region known as the Donbas.
"I would like to ask voters for a mandate to ensure the irreversibility of the country's European and Euro-Atlantic integration and our independence, as well as to restore Ukraine's territorial integrity, bring back peace, and complete the construction of a strong state capable of providing prosperity to every Ukrainian," Poroshenko said at a forum in Kyiv.
"We will submit a bid to join the European Union in 2024," Poroshenko said, adding that Ukraine would also take further steps to join NATO if he was reelected.
"Strengthening our armed forces and modernizing them…will remain our priority over the next five years," Poroshenko said. But with Russia keeping the pressure on, he said, "Only full EU and NATO membership would completely and irreversibly guarantee the independence of our Ukrainian state and Ukrainian national security."
Poroshenko, who critics say has failed to tackle pervasive corruption, also vowed that a special court to try corruption cases would be up and running this year. Western officials say graft is a huge hurdle to the prosperity and security of Ukraine.
In what was widely seen as an effort to bolster his sagging public support ahead of the election, Poroshenko spearheaded successful efforts to secure the creation of an independent Orthodox Church of Ukraine.
The incumbent president's popularity rating is low but polls suggest he and former Prime Minister Yulia Tymoshenko, who announced her presidential bid on January 22, are the likely front-runners.
Tymoshenko, who was a leader of the 2004 Orange Revolution, was defeated by Poroshenko in the 2014 presidential election.