Donald Trump has said he will rename Lake Ontario as Lake America in the US following the escalating trade war with Canada.
The US president signed an executive order on Thursday and said the change would take effect immediately.
It will only apply in the US, as Mr Trump cannot force Canada to follow the renaming.
Signing the order in the Oval Office, Mr Trump told reporters that Canada is "the worst" to deal with on trade, adding: "They feel entitled and we can't have that."
It comes after the Canadian government said it would impose new tariffs on the US earlier this week on what it said was $20bn (£17.1bn) worth of US goods.
Canada said the counter-tariffs would impose duties of 15%, 25% and 50% across 700 products, including steel and appliances, imported from south of the border, to match dollar-for-dollar new duties imposed by Washington.
Talks broke down between the sides last week, and the Trump administration implemented planned tariff increases on Canadian goods on Saturday, including alcohol, wood products and clothes.
Further tariff hikes on steel, cars and car parts were announced by Mr Trump on Monday, due to be introduced in January.
A war of words also broke out between the countries.
Doug Ford, premier of Ontario, Canada's most populous province, threatened to cut off electricity and mineral supplies to the US on Monday.
Mr Ford said Ontario powered 1.5 million homes and businesses in the US - and he warned that Mr Trump "better have a pack of batteries".
The official US-Canada border stretches across the water between Lake Ontario's northern and southern shores.
The body of water forms much of New York State's coastline and separates Buffalo from Toronto, the capital of the province of Ontario.
It comes after Mr Trump last year said he would be renaming the Gulf of Mexico as the Gulf of America - a move that was rejected by the Mexican government.
(c) Sky News 2026: Donald Trump signs order renaming Lake Ontario as 'Lake America' in the US
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