Stephen Harper and Barack Obama voiced objections behind closed doors during a Group of Seven summit to meetings that three European leaders have arranged with Vladimir Putin, private tête-à-têtes that they feel undermine efforts to isolate the Russian president.

A source with knowledge of the matter described the gulf that exists between the North American leaders and several European counterparts over whether to shun or engage Mr. Putin over his seizure of Crimea and efforts to destabilize Ukraine.

Mr. Harper and Mr. Obama asked what kind of message these meetings would send at a time when the West is trying to isolate Mr. Putin, the source said.

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The problem, the Canadian and U.S. leaders argued, was that G-7 countries are "on the one hand applying pressure but on the other hand meeting him and behaving as though things are normal."

Mr. Harper and Mr. Obama, both of whom are refusing to meet with the Russian leader during commemorations of the 70th anniversary of D-Day landings in France this week, then pressed the U.K.'s David Cameron, France's Francois Hollande and Germany's Angela Merkel to ensure they communicate the G-7's position firmly to Mr. Putin.

The request from Mr. Harper and Mr. Obama for these Group of Seven colleagues was that "if you want to meet with him, this is the message you must drive and you must drive it consistently ... here are the expectations and here are the consequences," the source said.

In a statement Wednesday night G-7 leaders repeated their condemnation of Russia's seizure of Crimea and efforts to destablize eastern Ukraine and said while existing sanctions remain in place they stand ready to intensify these penalties and add more punitive measures "should events so require."

Speaking to reporters following the G-7 meeting in Brussels Thursday, Mr. Harper insisted that Moscow remains diplomatically isolated from Western countries even though three Group of Seven leaders have arranged get-togethers with him in Normandy, France.

These tête-à-têtes will be the first face-to-face meetings with the Russian leader since he annexed Ukraine's Black Sea peninsula in March.

Mr. Hollande, who is also refusing to cancel the sale of state-of-the-art French warships to Moscow, will host two separate dinners Thursday – one for Mr. Putin and another for U.S. President Barack Obama who still refuses to meet his Russian counterpart.

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This socializing with Mr. Putin would appear to undermine the Group of Seven efforts to treat Russia as an international pariah for its unapologetic violation of Ukraine's sovereignty. It was only in March that G-7 leaders cut Russia out of the Group of Eight, effectively reducing their club to the Group of Seven.

Mr. Harper declined to say whether he approved or disapproved of the U.K., French and German get-togethers with Mr. Putin.

He instead noted it would be unreasonable to have barred the Russian leader from commemorations of the 70th anniversary of the D-Day landings given the country's huge role in the Second World War.

Mr. Harper said G-7 leaders agreed not to disinvite Mr. Putin to Normandy.

"There was an agreement that Russia should not be excluded from the Normandy celebrations because of the historic role of Russia, the then-Soviet Union, in the defeat of fascism in Europe. Obviously whatever contemporary difficulties we have with the current regime there, and they are obviously immense, I don't think we want to in any way diminish the Soviet and Russian contribution to the war effort which was obviously enormous at the time."

Many of Canada's European allies have big business, financial or energy ties to Russia. France is proceeding with a defence sale that will significantly bolster Russia's naval power while the United Kingdom is home to a wealthy Russian émigré population and Germany's investment and petroleum ties with Russia are significant.

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Mr. Harper said he's confident that any leaders who meet with Mr. Putin will press him on exiting Crimea and ending efforts to destabilize Ukraine.

"I am not meeting with Putin and I know Mr. Obama is not meeting with Mr. Putin," he noted.

He said the G-7 remains united on the need for Russia to back down and will keep in place sanctions against Mr. Putin's inner circle until this occurs.

"We had a very detailed discussion of that very issue and a very detailed discussion of the messages that need to be sent to Mr. Putin about ending illegal occupations, about ending provocative actions, ending the supporting of violent actions in eastern Ukraine and the necessity of the G-7 taking further action if those things are not done," the prime minister said.

"I think all of our allies are agreed that those messages, and only those messages, are the things that will be communicated to Mr. Putin."

Mr. Harper headed to France Thursday afternoon in preparation for D-Day commemorations June 6.