Prime Minister Mark Carney and Ukrainian President Volodymyr Zelenskyy spoke by phone Monday, reaffirming their agreement that Ukraine must be a party to any discussions about a possible end to the war in that country.

Speaking in advance of the Friday meeting in Alaska between U.S. President Donald Trump and Russian President Vladimir Putin, Carney and Zelenskyy welcomed Trump's leadership in working toward a lasting peace for Ukraine. 

"The two leaders underscored that decisions on the future of Ukraine must be made by Ukrainians [and] international borders cannot be changed by force," said a statement detailing the discussion that was released by the Prime Minister's Office.

The statement also said Ukraine's allies must continue to keep pressure on Russia to end its aggression and that any peace deal must include a "robust and credible" security guarantee.

Trump announced in a social media post on Friday that he would be meeting with Putin in Alaska on Aug. 15. 

Russia, which launched a full-scale invasion of Ukraine in February 2022, now holds nearly a fifth of the country.

In addition to Crimea, which it seized in 2014, Russia has formally claimed the Ukrainian regions of Luhansk, Donetsk, Kherson and Zaporizhzhia as its own, although it controls only about 70 per cent of the last three. 

Russia also holds smaller pieces of territory in three other regions, while Ukraine says it holds a sliver of Russia's Kursk region.

Zelenskyy could attend second meeting, says Trump

"I am grateful for Canada's support for Ukraine and our people," Zelenskyy said in a social media post after speaking with Carney. "We agreed that no decisions concerning Ukraine's future and the security of our people can be made without Ukraine's participation."

Zelenskyy expressed skepticism that Putin genuinely intends to end his invasion of Ukraine, saying it's obvious "the Russians simply want to buy time."

The Ukrainian president said that until his country is invited to the negotiating table and Kyiv is given security guarantees, "sanctions against Russia must remain in force and be constantly strengthened."

Trump told a White House news conference Monday that his Friday meeting with Putin will be a "feel-out meeting" to gauge whether the Russian president is really willing to make a deal. 

"So I'm going in to speak to Vladimir Putin, and I'm going to be telling him; 'you've got to end this war. You've got to end it,'" Trump told reporters.

Trump also said a future meeting between himself and Putin could include Zelenskyy. He said he would speak to  European leaders soon after his talks with Putin and that his goal was a speedy ceasefire in the bloody conflict.