President Donald Trump announced Thursday that Lake Ontario will be renamed “Lake America” within the United States, the latest move in an escalating trade war with Canada.

The Republican president signed an executive order directing the Interior Department to update the lake’s name in the U.S. geographic naming service. The order cannot force Canada to follow along, however. On the U.S. side, the change will flow through the Geographic Names Information System, the federal database that standardizes names on government maps and documents, and its practical reach will depend on whether federal agencies, commercial mapmakers and other governments adopt the new name.

Trump had been floating the idea of the name change in recent days, as the U.S. announced it was imposing 50% tariffs on $20 billion worth of Canadian goods over the weekend after talks between the countries broke down. Trump has been needling America’s northern neighbor since he returned to the White House last year, suggesting the ally with whom the U.S. once had warm relations should instead be absorbed as the 51st state.

Canada responded to Trump’s import taxes this week by imposing retaliatory tariffs on $20 billion worth of American goods, including steel, dairy products, appliances, and farm equipment.

Oval Office signing ceremony

Trump signed the order while sitting at the Resolute Desk in the Oval Office. Behind him, a large sign propped on a stand displayed a map of the Great Lakes, with “Lake America” written in big red letters over Lake Ontario. On the other side of the president stood another map bearing the words “MAKING THE GREAT LAKES EVEN GREATER.”

Trump said as he was signing the order that he’d “notified all of the various people that we have to notify. So, we’ve done everything that you have to do.”

“And this is official, effective immediately,” he added.

The executive order Trump signed, however, specifies that the changes are supposed to be made within 30 days.

Canadian officials dismiss the move

Canadian officials dismissed Trump’s move.

Canadian Prime Minister Mark Carney rejected the renaming, invoking the lake’s Indigenous roots and noting that the name predates both Canadian Confederation and the U.S. Declaration of Independence.

“Canadians also know that naming reality means calling it Lake Ontario — then, now and always,” he wrote.

Ontario Premier Doug Ford, who has traded insults with Trump, said on X: “It’s Lake Ontario to Canadians and the rest of the world. Now and forever.”

Nova Scotia Premier Tim Houston said, “We’re into some real foolishness now. It’s Lake Ontario, buddy.”

The lake is one of multiple Great Lakes that the U.S. and Canada share borders along. Lake Ontario is the smallest of the five by surface area and the easternmost, draining toward the Atlantic through the St. Lawrence River. Together the Great Lakes hold roughly one-fifth of the world’s surface fresh water and are managed jointly under the 1909 Boundary Waters Treaty, which created the binational International Joint Commission to regulate shared waters, including Lake Ontario’s outflows — arrangements the executive order leaves unchanged.

New York Gov. Kathy Hochul, a Democrat whose state shares a border on the lake, wrote on X in response to the White House’s announcement: “New York won’t be calling it that.”

There is no single international body that determines the names of international bodies of water, and Trump has wide latitude over how the U.S. government recognizes geographic places and landmarks.

The name Lake Ontario comes from the Huron Indigenous people’s word “oniatarí:io,” which means “lake of shining waters.” The province of Ontario, founded in 1867, took its name from the lake.

Trump denies geopolitical message, renews criticism of Canada

Trump said that while his action was not meant to send any particular geopolitical message, “Canada’s been ripping us off for a long time” on trade and military issues.

“They wanted to be treated like a state and they’re not a state,” the president said. “We just can’t do that anymore.”

“We love the people of Canada,” Trump added. “I don’t think their representatives do, an appropriate job. Maybe they’ll change. I really don’t know. It doesn’t make much difference.”

The move is reminiscent of his decision last year to rename the Gulf of Mexico as the “Gulf of America,” a day-one executive order that also restored the name Mount McKinley over Alaska’s Denali. That change altered U.S. federal usage and was picked up by major American mapping platforms, while Mexico refused to recognize it — and the White House barred Associated Press journalists from presidential events after the wire service kept “Gulf of Mexico” in its style guidance, a restriction a federal judge later ordered lifted.

Trump scribbled his name with a Sharpie pen on the executive order, then held it up for the cameras, offering, “And we filed all the necessary papers, documents, everything else.”

He also suggested his push to rename bodies of water may not be finished.

“So, if you think about it, we have a gulf and we have a lake. Now, all we need is an ocean,” Trump said. “So maybe we’ll have to change the name of the Atlantic and/or the Pacific. Maybe we’ll change them.”

---

Associated Press writer Rob Gillies in Toronto contributed to this report.

This story was originally featured on Fortune.com.