The date for a trilateral summit between the leaders of Canada, the U.S. and Mexico appears to have moved. 

It's Canada's turn to host the North American Leaders' Summit, and security officials were actively planning for it to happen in February. 

The last so-called Three Amigos summit was held in Mexico in February 2014. Canada hasn't hosted one since 2007, when it was held in Montebello, Que.

"President Obama and President Peña Nieto welcome Prime Minister Harper’s offer for Canada to host the next North American Leaders’ Summit in 2015," a joint declaration said last year.

In December, Canadian security officials learned the date would be changed to the fall. No further explanation was provided.

In a statement, the Prime Minister's Office said the summit will happen later in 2015.

"We have not announced a date for the meeting. We intend to host the meeting later in the year," said spokesman Jason MacDonald.

No specific location had been confirmed for Canada's meeting.

Summit dates prone to change

There is no fixed time of year for the three leaders to meet. Dates for the summit have been prone to change.

The three countries rotated hosting duties between 2005 and 2009, but in 2010, Canada postponed a meeting that had been scheduled to be held in Wakefield, Que., and then did not host it at all.  

The summit scheduled for Hawaii in November 2011 was postponed following the sudden death of Mexico's interior secretary. U.S. President Barack Obama hosted his counterparts the following April in Washington. 

There was no summit in 2013.

If the Stephen Harper government sticks to its fixed election date, the next federal election will be on Oct.19.

Although speculation is rife that the Conservatives may prefer to go to the polls early, the PMO has given no official indication that could happen.

In Washington Thursday, White House spokesman Josh Earnest said he didn't know exactly why the summit was postponed and he was "not really" concerned as long as it gets rescheduled in a timely fashion. He joked that the weather would be better later in the year. 

Tactical postponement?

Given the fixed election date, former diplomat Colin Robertson, now based in Ottawa with the Canadian Defence and Foreign Affairs Institute, thinks a new date in November is most likely.

"It would be an anomaly not to have it at all," he says, despite Canada's track record of not hosting in 2010.

'It will raise in both minds, how committed is Stephen Harper to trilateralism?'- Colin Robertson, former diplomat

For his American and Mexican counterparts, Harper's decision not to host this winter or spring should be "not a surprise and not unexpected," Robertson says.

Last summer, Harper's ministers were taking plenty of shots at the Obama administration — over the Keystone XL pipeline, food labelling and a range of other issues.

But the need to put up a more unified front on things like the fight against ISIS or the crisis in Ukraine compelled Harper and Obama to keep "on a more even keel" since then, Robertson says.

Obama spokesman Earnest downplayed Canada-U.S. tensions Thursday, saying the relationship is "far deeper and far broader than this one infrastructure project," and there is certainly a lot more for the countries to discuss than just the Keystone XL pipeline.

"I'm not particularly worried about any sort of Keystone outcome looming over those meetings at all," said Earnest. He added that U.S. and Canadian government officials are frequently in touch by phone.

Wants to look 'prime ministerial'

For Mexico, Canada's unwillingness to budge on their visa requirements remains a barrier to a harmonious summit, despite more recent efforts to fast-track Mexican visa applications.

"They want the summit to go well and if the backdrop is clouded with an election looming," Robertson says, "Harper will have no interest in a summit where he doesn't look... prime ministerial."

The other two leaders will understand that tactically, he says. The date is Canada's call.

Nevertheless, cancelling it outright would be a strategic error, Robertson thinks.

Shared energy and environmental concerns leading up to the UN climate change summit in Paris, as well as shared trade interests like the automotive and agriculture negotiations key to the Trans-Pacific Partnership talks, are among the top-level discussions the leaders need to convene at some point.

The later date tips Harper's hand in terms of his priorities.

"It will raise in both minds, how committed is Stephen Harper to trilateralism?" he says.

With files from Janyce McGregor