WASHINGTON (AP) — President Donald Trump said Thursday he is renaming Lake Ontario to be known as "Lake America" in the United States as he escalates his 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. Trump cannot force Canada to follow along, however.

Trump has 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.

Trump, who signed the order as he was sitting at the Resolute Desk in the Oval Office, had a large sign behind him propped on a stand with a map of the Great Lakes. Over Lake Ontario, in big red letters, the map read "Lake America."

On the other side of the president was another map with 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.

But the executive order Trump signed shows that the changes are supposed to be made within 30 days.

Canadian officials dismissed Trump's move.

Canadian Prime Minister Mark Carney rejected the move, 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. 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 that, "New York won't be calling it that."

There is no single international body that determines 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 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 move last year to rename the Gulf of Mexico as the "Gulf of America."

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."