"Ukraine's stand is as follows: we will deal with Donetsk and Luhansk representative legitimately elected under Ukrainian law," Poroshenko wrote in his Twitter.
Donetsk and Luhansk's special status is one of 13 conditions agreed to last month in Minsk. Previous attempts to grant these regions legal status were made in talks in the Belarusian capital last fall, but were scrapped by winter.
The measure is part of the latest effort to end the 11-month conflict in the region that the United Nations documents has to date claimed over 6,000 lives.
Moscow has expressed concern that despite Kiev's undertaking to devolve its powers to southeast Ukraine ahead of constitutional reform expected by the end of 2015, Poroshenko's proposal is crammed with unnegotiated amendments and preconditions.