The influential German leader will be in Washington earlier Monday for a previously scheduled meeting with U.S. President Barack Obama, amid reports of a rift between the U.S. and Europe over whether to arm Ukraine's military.
Merkel's supper hour arrival in Ottawa for talks with Harper afterwards will allow the prime minister to receive a private briefing from a trusted ally who is at the centre of a pivotal moment in the West's renewed push to end the continued fighting in eastern Ukraine.
Ukraine's military has been battling Russian-backed separatists since April in a conflict that the United Nations says has killed 5,300, a figure that has spiked in recent weeks.
Merkel, French President Francois Hollande, Russian President Vladimir Putin and Ukrainian President Petro Poroshenko spoke by telephone Sunday and are attempting to hold a summit this Wednesday in the Belarus capital of Minsk.
Merkel also travelled to Moscow on Friday to meet with Putin, amid reports that the U.S. is considering arming Ukraine forces, which France and Germany oppose. Canada has not committed to arming Ukraine forces either.
Harper has taken a harder line towards Putin than his fellow G7 leaders, and a senior government source says that's not likely to change.
But the source, who was not authorized to speak on the record, says Harper is eager to get an update from Merkel on the Ukraine-Russia standoff.
"He will be very interested in hearing her take on those discussions," said the source.
"I don't anticipate any phone calls between the prime minister and Mr. Putin any time soon."
Harper made a point of avoiding Putin last summer when the two were in France for the 70th anniversary celebrations of the Normandy invasion that led to the end of the Second World War.
In November at the G20 summit in Brisbane, Australia, Putin approached Harper and extended his hand when he was talking to a group of fellow leaders.
"I guess I'll shake your hand but I have only one thing to say to you: You need to get out of Ukraine," Harper told Putin, according to the prime minister's spokesman, Jason MacDonald.
Putin's reply, according to a Russian spokesman, was: "That's impossible because we are not there."
Putin left the summit early, but not before meeting with British Prime Minister David Cameron and Hollande.
While it appears Canada won't be playing any direct role in this latest round of talks between Putin and the West, the Harper government will continue to "work in concert with our allies as we always have," said the source.
Canada has a long tradition of being an add-on to the travel of world leaders doing business in Washington.
But the source said Harper places top value on his relationships with his fellow G7 leaders and had always extended an open invitation for them to drop by, informally if necessary, while making their inevitable visits to Washington.
In August 2012, Merkel paid a two-day visit to Canada that started with an evening of private discussion on the world economy at the prime minister's Harrington Lake, Que., retreat before more formal talks at his Parliament Hill office the following morning.
This time, Merkel wanted another chance to talk to Harper face to face, just not with the bells and whistles of a regular visit, the source explained.
"She's in Washington, she's close, she wants to be able to come and it not to be a big imposition on time," said the source. "They've asked for the meeting."
Germany's chairmanship of the G7 to be held later this spring in Bavaria, the continuing fight against the Islamic State in Iraq and Syria, and the global economy will all be up for discussion during Merkel's Monday night working dinner in Ottawa, said the source.
Merkel is expected to begin her return trip to Europe before the evening is out.
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