Canada has spearheaded a G7 foreign-ministers' statement that condemns Russian aggression in Ukraine and urges the release of detained sailors, Foreign Affairs Minister Chrystia Freeland says.

The joint communique says the foreign ministers of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States, and the high representative of the European Union, are concerned about Russia's actions against Ukraine in the Kerch Strait and surrounding waters.

The leaders are urging restraint, respect for international law and no further escalation.

They are calling on Russia to release the detained crew and ships and refrain from impeding lawful passage through the Kerch Strait. The strait separates Crimea — Ukrainian territory Russia seized in 2014 — from the Russian mainland and allows ships to reach Ukrainian ports.

On Sunday the Russian coast guard opened fire and seized three Ukrainian vessels, including their crew members.

"Canada has indeed, this week, been very active on the tensions between Ukraine and Russia," Freeland told reporters in Buenos Aires Friday, where she's part of the Canadian delegation at a G20 summit.

She said Canada, which is president of the smaller and more exclusive G7 until the end of 2018, worked hard to ensure the statement was released today so that the position of the G7 on this issue would be clear as leaders meet.

"The G7 is united in condemning this Russian aggression, is united in calling for the release of those 24 sailors who are prisoners of war, is united in calling for the vessels to be released and is united in standing for Ukraine's sovereignty and territorial integrity," said Freeland.

The statement also says the G7 countries will never recognize Russia's illegal annexation of the Crimean peninsula.

Canada's strong voice

The joint message comes two days after Russia announced it would deploy another battery of anti-aircraft missiles to Crimea, bolstering its hold on the region.

There had been mounting pressure on Canada from top Ukrainian officials to forge a diplomatic front against Russia's actions.

Andriy Shevchenko, the Ukrainian ambassador to Canada, had said that Prime Minister Justin Trudeau should use Canada's position as G7 president to deal with the current crisis.

Shevchenko said Friday that he was "very satisfied" with the statement.

"We see clear wording, we see empathy and we feel support toward Ukraine based on international law. I would also like to acknowledge very impressive Canadian leadership on this issue within the G7 community," he said in an interview.

Shevchenko said the statement is a result of trustworthy and meaningful communication between the Ukrainian government and the Canadian government.

Freeland said she spoke with Ukraine's foreign minister, Pavlo Klimkin, and Trudeau spoke with Ukrainian President Petro Poroshenko on Thursday.

"President Poroshenko specifically said he was very glad to have the chance to speak to our prime minister on the eve of the G7 meeting and I'm not in the room right now but Canada certainly anticipates that this will be an important issue in those conversations," Freeland said.

"Canada will speak, as we have in leading this G7 foreign ministers' statement, with a strong voice and a voice on this issue where we are rightly, I believe, considered to have a real expertise," said Freeland.

U.S. President Donald Trump announced Thursday on Twitter he would not meet Russian President Vladimir Putin when both are in Argentina because "the ships and sailors have not been returned to Ukraine from Russia."

Freeland said she had spoken with U.S. Secretary of State Mike Pompeo about Ukraine and that Canada collaborated with all G7 partners "very much including the United States" on the statement.