TORONTO - Prime Minister Stephen Harper says he is "deeply concerned" about the conviction of a Ukrainian opposition politician and has written a letter to President Viktor Yanukovych.

Yulia Tymoshenko, a popular opposition leader in Ukraine, was convicted of abuse of office and sentenced to seven years in prison.

Speaking to the Ukrainian Canadian Congress on Friday night in Toronto, Harper said Tymoshenko's situation "may have serious consequences" for the relationship between Canada and Ukraine.

Harper says the conduct of Tymoshenko's trial didn't reflect accepted norms of due process or fairness.

Tymoshenko was convicted over her handling of a gas import contract in 2009, but she says the trial is an attempt by longtime political foe Yanukovych to bar her from coming elections as a convicted felon.

Harper says Canada will support Ukraine whenever it moves toward freedom, democracy and justice.