Japanese officials say they believed they were also negotiating with Canada and Mexico when they struck a controversial side agreement with the United States on automobiles last year during the Trans-Pacific Partnership talks.
They discussed that agreement with U.S., which angered Canada and Mexico, in a briefing ahead of a Friday meeting between Foreign Affairs Minister Stephane Dion and his Japanese counterpart, Fumio Kishida.
The Japan-U.S. deal on rules of origin in the auto sector would have allowed a higher percentage of Japanese parts in cars in North America's highly integrated industry. The fallout stalled completion of the 12-country Pacific Rim deal by at least two months.
The Japanese officials say they were surprised to learn that they had negotiated a deal with only the United States.
Mexico's former ambassador to Canada has said the side deal angered the Canadians and Mexicans and nearly drove the two countries from the bargaining table.
But the Japanese officials, who briefed journalists on the condition they not be named, said their government didn't think they were doing anything to snub Canada and Mexico.
"We thought that the U.S. represented Canada and Mexico," said one.
They did not explain why they thought the United States was negotiating on behalf of Canada and the Mexico. "We were very surprised" to learn "Canada had not been consulted by the U.S.," said one official.
Mr. Kishida, during a joint news conference with Mr. Dion, deflected a question on the issue.
"There was very tough negotiations that were conducted," he said through a translator.
"They have reached a conclusion that everybody's comfortable with."
Matthew McAlvanah, a spokesman for the United States Trade Representative, said Friday his government "played a leadership role in the TPP, working diligently with the other parties to develop strong rules of origin."
The Liberal government signed the TPP earlier this month in New Zealand, but says it will not formally ratify the deal it inherited from the Harper government until it consults Canadians and puts it to a vote in Parliament.
The Japanese officials said their country has no official timetable for ratification, but there is hope that might occur by the end of June.
Japan hosts this year's G7 summit, and Mr. Dion and Mr. Kishida have a broad agenda that also includes combating terrorism, nuclear proliferation and climate change.
Mr. Kishida's visit is the first visit to Canada by a Japanese foreign minister in 20 years.
Mr. Dion and Mr. Kishida met in November at the APEC summit in Manila and struck up a good rapport, said the Japanese officials.
Japan is interested in the Trudeau government's desire to return Canada to United Nations peacekeeping missions.
Japan currently has more than 350 engineers deployed to mission in South Sudan and would like to discuss partnerships with Canada "to build capacity" of UN operations in the future.
Prime Minister Justin Trudeau has said he wants Canada to make specialized contributions to future peacekeeping missions by supplying experts such as engineers and medical personnel as well as French speakers, but not infantry.