OTTAWA, Aug. 9 -- Canada's ambassador to the United States David MacNaughton said Thursday that he will leave his post at the end of the month.

"Serving as Canada's ambassador in Washington, at this pivotal time in our country's history, has been the greatest honor of my life," said MacNaughton in a statement.

MacNaughton, who has been a vital player in the Canadian government over the past few years, helped negotiate the North American Free Trade Agreement, which Canadian Prime Minister Justin Trudeau states is "historic" to Canadians.

After his resignation, MacNaughton will return to Toronto and start to take up "new challenges in the private sector," according to his statement.