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.

On Saturday, Google said it had changed the name on its maps for users in the US.

"Since we update Google Maps to reflect name changes in official government sources, which is GNIS [Geographic Names Information System] for the US, people using Maps in the US will see 'Lake America', those in Canada will continue to see 'Lake Ontario' and those outside of the US and Canada will see both names," the tech firm said in a blog post.

This mirrors how Google names the Gulf of Mexico for users after Trump declared it was called the Gulf of America in 2025.

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 trademark 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.

Mexico similarly rejected Trump's renaming of the Gulf of Mexico to the Gulf of America, arguing a single country could not rename a shared body of international water.