Washington DC - President Donald Trump on Tuesday said Canada could join his "Golden Dome" plan either by paying $61 billion or by becoming part of the US.

"I told Canada, which very much wants to be part of our fabulous Golden Dome System, that it will cost $61 Billion Dollars if they remain a separate, but unequal, Nation, but will cost ZERO DOLLARS if they become our cherished 51st State," Trump wrote on his Truth Social network.

"They are considering the offer!"

His comments came shortly after Canadian Prime Minister Mark Carney told the CBC that he wants to sign on to a major European defense initiative by July 1, a move aimed at reducing the country's reliance on the US for weapons and munitions. He had previously expressed interest in joining the Golden Dome project.

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But the Liberal has also consistently rejected Trump's aggressive moves to annex Canada, insisting at a recent Oval Office meeting that "Canada is not for sale."

Last week, Trump unveiled more details about the $175 billion project, saying it would be operational before the end of his term in 2029 and capable of intercepting drones and missiles from anywhere in the world, and even from space.

Aside from its huge cost, the scheme has also drawn sharp condemnation from other countries for stoking a dangerous global arms race.