Poroshenko, who spoke through an interpreter during a one-day visit to Finland Tuesday, didn't elaborate.
Last month, a municipality on Sweden's strategic Baltic Sea island of Gotland turned down a Russian request to rent harbor space after the government warned it could harm the Scandinavian country's defense and political interests. Russian energy giant Gazprom wanted to store pipes in Slite harbor for the pipeline called Nord Stream 2.
In Helsinki, Poroshenko met with Finnish counterpart Sauli Niinisto. On Monday, he was in Estonia.