Washington DC - President Donald Trump called Canadian Prime Minister Mark Carney the "future Governor of Canada" in a bizarre social media rant about invasive Asian carp in Lake Michigan.

Trump has repeatedly hinted at making Canada the US' 51st state, and he picked up the theme again in a a Truth Social post on Tuesday.

"I'm working with Governor Gretchen Whitmer on trying to save the Great Lakes from the rather violent and destructive Asian carp, which is rapidly taking over Lake Michigan and all of the beautiful surrounds," he wrote.

"I'll be asking other governors to join into this fight, including those of Illinois, Wisconsin, Minnesota, Pennsylvania, Ohio, Indiana, New York, and, of course, the future governor of Canada, Mark Carney, who I know will be happy to contribute to this worthy cause."

Trump's threats to annex Canada started even before he re-entered office last year, triggering a major spat with former Prime Minister Justin Trudeau during the last months of his premiership and indirectly leading to a spike in popularity for Carney, who stormed to a surprising election win off the back of a message emphasizing Canadian sovereignty.

In January, Trump trolled Canada, Venezuela, and Greenland by posting an edited photo showing a map in which all three countries are covered in the American flag.