(Adds details from Trudeau office's statement, background, byline)
OTTAWA, April 12 (Reuters) - Canadian Prime Minister Justin Trudeau will break off a foreign trip to return to Ottawa for a meeting on Sunday with the premiers of two provinces arguing over an oil pipeline, his office said on Thursday.
The unexpected development is a sign of the pressure building on Trudeau to solve a dispute which could turn into a constitutional crisis.
Trudeau's federal Liberals are pitted against the Pacific province of British Columbia, which opposes plans by Kinder Morgan Canada to almost treble the capacity of its Trans Mountain pipeline from Alberta to the west coast.
Trudeau left Ottawa on Thursday for a nine-day trip, starting with a regional summit in Peru on Friday and Saturday.
"The Prime Minister will be returning to Ottawa following his visit to Peru to convene a meeting on Sunday, April 15 with the premiers of Alberta and British Columbia to discuss next steps for moving the Trans Mountain expansion project forward," said the statement. It gave no further details.
Ottawa, which approved the project in 2016, insists it has jurisdiction. But the British Columbia government disagrees, citing the risk of a spill.
Kinder Morgan Canada, fed up with the delays, is threatening to walk away unless the dispute is settled by May 31.
"I wouldn't approve major pipeline projects if I wasn't confident they could be done safely," Trudeau said in a video released on Thursday.
It is rare for different levels of government in Canada to argue so openly over resources and Trudeau is under pressure to reassert Ottawa's authority. Energy industry analysts say that unless the dispute is settled, Canada will become a much less attractive place for foreign investment.
Alberta Premier Rachel Notley, who is threatening to cut oil supplies to British Columbia, said on Monday that if Trudeau did not step in, "the reverberations of that will tear at the fabric of (Canada) for many, many years to come."
A well-placed source said on Wednesday that Trudeau would put pressure on British Columbia to drop its resistance but will try to avoid tougher measures that might alienate voters who helped his Liberals win power.
British Columbia says Ottawa should refer the matter to the Supreme Court for clarification. Cabinet ministers have dismissed the idea, saying it was already clear the federal government has jurisdiction over major pipelines. (Reporting by David Ljunggren; Editing by Dan Grebler and Richard Chang)