Ukraine's envoy says his government is growing concerned about whether Canada will continue its military support to help the country deter Russian aggression.

The mission is set to expire at the end of March.

But with thousands of U.S. troops arriving in Poland and neighbouring countries to bolster NATO forces, Ukraine — not a NATO member — is anxious to see an extension of Canada's commitment to it.

"It has taken us much longer than we expected to discuss the future format of our co-operation," Andriy Shevchenko, the Ukrainian ambassador to Canada, said in an interview. "We still don't have a formal response from Canada."

A spokeswoman for Defence Minister Harjit Sajjan offered no further clarification on Friday, saying in an email: "The announcement will come after cabinet has made a decision."

Shevchenko suggested Canada might be more carefully weighing its military contributions to the West's deterrence of Russia in eastern Europe in light of its upcoming responsibilities in Latvia.

The sooner a decision is made, he said, the sooner it will serve its purpose as deterrence to Russia.

"It could also be a very important signal to Russia," he said. "Those people who sit in the Kremlin and plan their other terrible activities in Ukraine, the sooner they learn that the West and Canada is serious about future co-operation, the better it is."

Canada will be deploying 450 troops to Latvia in the coming months to form the core of a 1,000-plus battle group that will include troops from Spain, Albania, Italy, Poland and Slovenia.

Understanding Russian tactics

That is part of a broader NATO effort in which Germany, the United States and Britain will lead their own battle groups in Lithuania, Poland and Estonia.

Those people who sit in the Kremlin and plan their other terrible activities in Ukraine, the sooner they learn that the West and Canada is serious about future co-operation, the better it is. - Andriy Shevchenko , Ukrainian ambassador

Ukraine is not a NATO member but Russia's annexation of its Crimea region in 2014 was the trigger for the current political crisis between the West and Russia, their worst since the end of the Cold War.

"Obviously we would like to see clarity on this issue as soon as possible," said Shevchenko.

He said Canadian troops are also gaining valuable new experience from the Ukrainian counterparts they are supporting, including a better understanding of disruptive Russian tactics including cyberwarfare.

"We know the tools the Russians have been using against the free world when it comes to cybersecurity, and we would like to share this knowledge with Canada and the free world."