Ontario Premier Doug Ford has hit back at Donald Trump by installing a large sign on Canada's shoreline with the message: "Lake Ontario. Now and Always."

The US president signed an executive order on Thursday seeking to change its name to Lake America and has shared a series of AI-generated videos about the lake that straddles both countries.

"Long before President Trump, this lake was called Lake Ontario. Long after President Trump is gone, it will still be called Lake Ontario," Ford said.

The war of words was triggered after trade talks collapsed, with the US imposing new 50% tariffs on $20bn (C$28bn) of Canadian goods. Canada will implement "dollar for dollar" counter-tariffs next month.

Trump said the decree was effective immediately as he signed the order to rename it Lake America.

While he has broad discretion over how the US recognises landmarks, other countries are not required to follow. Canadian officials have dismissed Trump's move.

On Saturday, Trump also posted several AI-generated videos on social media, with one showing him kicking over a Lake Ontario sign and replacing it with one that says: "Welcome to Lake America."

Another video depicted a flock of Canada geese sporting the US president's hair and holding rifles as they patrolled the shoreline of a newly named Lake America.

Ford said Trump's renaming of the lake was because he "didn't like Ontario and Canada standing up for ourselves".

Standing in front of the newly unveiled Lake Ontario sign, Ford added: "Just in case President Trump or anyone else forgets, we've set up this sign to remind them, it's Lake Ontario, now and forever."

It echoes Canadian Prime Minister Mark Carney's previous response to the row, insisting "things must be called by their name, and this lake is called Lake Ontario - today and forever".

The names of four of the Great Lakes - Ontario, Huron, Michigan and Erie - originate from indigenous words. Lake Superior was named after an anglicised French word. Lake Ontario, the smallest of the Great Lakes, borders both the Canadian province and the US state of New York.

Trump's executive order gives the US Department of the Interior 30 days to update the name change with the Geographic Names Information Service - the official repository of domestic geographic names in the US.

When Trump entered the White House in 2025, he signed a similar order that changed the Gulf of Mexico to the Gulf of America. Mexico has rejected the name change, arguing a single country cannot rename a shared body of international water.

It also led to a legal dispute between Mexico and tech giant Google, which renamed the gulf in its maps application.

In that case, Google Maps users in the US see "Gulf of America", while those in Mexico see the "Gulf of Mexico". Those in other countries see the "Gulf of Mexico (Gulf of America)".