"In autumn there will be a new parliament that will start on reforms," Poroshenko said in a televised interview.
A new vote has been widely expected since the dissolution of the ruling majority coalition in parliament last week paved the way for Poroshenko later this month to call fresh polls.
There has been a loud clamour to bring forward the elections -- originally scheduled for 2017 -- ever since the ouster of Kremlin-backed leader Viktor Yanukovych in February following months of bloody protests.
The vote however comes at a perilous time for Ukraine as government forces wage a brutal war against pro-Russian separatists in the east of the country.
The country's top military brass has pledged a quick end to a military offensive that has cost over 1,100 lives since mid-April, but they face a mammoth task in subduing the well-armed insurgent fighters.
Top political leaders have agreed to shorten the pre-election campaign to 45 days but nonetheless the prospect of a fresh vote is expected to spark a period of bitter squabbling among Ukraine's fractious political rivals.