In an unusual move, Harper has written an editorial on the situation in Ukraine that was published in Saturday's Globe and Mail.
He writes that although militants in eastern Ukraine are referred to as 'pro-Russian separatists,' there is no doubt they are "an extension of the "Russian state."
Harper accuses Russia of "aggressive militarism" that he says is a threat to not only Ukraine, but Europe and the values that bind Western nations.
Some Canadian companies, notably aircraft maker Bombardier, have expressed concern about doing business in Russia in the face of increasing Canadian sanctions on Russian individuals and entities.
Harper says Canada's national interests must come first.
"The steps Canada has taken have not been made without careful consideration of their potential impact on Canadian business interests abroad and at home," Harper writes.
"We will not allow business interests alone to dictate our foreign policy."
Bombardier said Friday that Canadian sanctions could affect the timeline of the company's plans to set up a plant in Russia to build regional jets in a project estimated to be worth $3.4 billion.
Harper's editorial also raised the shooting down of a Malaysian Airlines plane this month, killing nearly 300 people including a Canadian.
He pointed the finger at militants in the Ukraine and said whether accidental or not the blood of the victims is on their hands.
Canada is sending an RCMP officer to the Netherlands on Sunday to determine how Canada can assist Dutch authorities in their investigation of the Malaysian air disaster _ they're taking the lead because many of those aboard were from the Netherlands.
Defence Minister Rob Nicholson offered the support on Saturday when he spoke with his Dutch counterpart, Jeanine Hennis-Plasschaert.
A statement from Nicholson's office said Canada will take part in a meeting this week hosted by Dutch officials regarding the next steps for victim identification and the investigation.
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