The Prime Minister's Office says in a release that Poroshenko thanked Canada for the support provided to Ukraine in recent months, and Canada's participation in upcoming military training exercises.
Poroshenko told Harper the recent capture of two members of the Russian Special Operations Force in Ukraine is further evidence of direct Russian involvement in the region.
And the statement says both leaders agreed that the Russian aggression in Ukraine must be met with economic sanctions.
Canada has all but severed relations with Russian President Vladimir Putin, save for a brief handshake between Harper and Putin at last year's G20, when the prime minister told the Russian leader flatly to get out of Ukraine.
In addition to imposing a series of sanctions against individuals and entities in both Russia and Ukraine, Canada has provided non-lethal military equipment to the Ukrainian government and provided humanitarian support and assistance to the civilian population.