President Rodrigo Duterte of the Philippines lashed out at Canada this week, provoked by a dispute between the nations that has festered for half a decade, over hundreds of tons of Canadian trash brought to Philippine ports.

“Canada, I want a boat prepared. I’ll give a warning to Canada, maybe next week, that they better pull that thing out or I will set sail,” he said at a news conference in San Fernando city in the Philippines on Tuesday.

He added: “We will declare war against them.”

In the days following Duterte’s remarks, Canada’s government responded, saying, in effect, that it was working on resolving the dispute — a business transaction gone wrong that has spiraled outward over the years and now touches on not only Philippine-Canadian relations, but also on an international treaty and Canada’s reputation abroad.

The trash in question arrived in 2013 and 2014, in 103 containers delivered from Canada by a private company and marked — falsely, Philippine officials say — as holding recyclable plastic scrap. In reality, dozens of containers held used adult diapers, household garbage, plastic bags and other waste, and some of the containers were found to be “leaching fluids,” according to a legal opinion on the case by the Pacific Centre for Environmental Law and Litigation, a Canadian nonprofit.

In 2016, a Philippine court ordered the company, Chronic Inc., to take the garbage back to Canada — but the waste stayed in port storage facilities, except for 26 containers that were dumped into a Philippine landfill. On Tuesday, Duterte threatened Canada that he would return the remaining trash one way or another. “Celebrate, because your trash is coming home,” he said. “Prepare a grand reception. Eat it if you want to.”

Caroline Thériault, a spokeswoman for Canada’s minister of environment, responded to Duterte’s taunts.

“We are working closely with the Philippines to resolve this issue in an environmentally responsible way,” Thériault said. A group of officials from both countries was “examining the full spectrum of issues,” she said.

Thériault said that in 2014, Canada did not have regulations in place to require the company to recover the waste. In 2016, Canada amended those rules to create criminal liability for companies and compelled them to take back the waste, but the case in the Philippines has remained in limbo — at least publicly — as officials met to discuss finding, paying for and disposing of the trash.

In 2017, Prime Minister Justin Trudeau of Canada said at a news conference in the Philippines that the “legal barriers and restrictions” that had prevented the government from recovering the garbage had been addressed, so it was “now theoretically possible to get it back.”

But he added, “There’s still a number of questions around who would pay for it, where the financial responsibility is. This was, at its origin, a commercial transaction. It did not involve government.”

Philippine activists and Canadian environmental groups have urged Canada to recover the trash for years, with some saying that, by failing to recover it, Canada has violated the Basel Convention, the treaty that regulates the export of hazardous waste.

Because Canada has not taken back the waste or paid for its return, “there’s a very good argument that they’re in violation of the convention,” said Dayna Scott, a law professor at York University in Toronto.

The convention lacks effective enforcement measures, however, and Canada has, so far, declined to support an amendment to the treaty that would forbid the movement of hazardous waste from developed nations to developing ones, Scott said.

Opponents of the amendment have argued that many developing countries want shipments of recyclables to turn into new products, while its supporters in the Philippines and Canada have pointed to the trash dispute as an example of what can go wrong.

Scott said that the dispute, by “exposing the positions that Canada is actually taking on the international stage, in terms of pollution,” has the potential to be a black eye for Trudeau, who has made confronting climate change a priority and sought to restore Canada’s status as a global leader on environmental protections.

The Philippine case “does kind of hit a nerve,” Scott said. “Philippine activists are saying, ‘We’re not your trash bin.’”