Kirsten Hillman, Canada’s longtime ambassador to the U.S., is stepping down

Kirsten Hillman, Canada's longtime ambassador to the United States, is leaving her post in the new year — marking a key shakeup amid tense trade relations with U.S. President Donald Trump's administration.

Hillman announced the move Tuesday in a social media post, where she also said she will "remain available" to Canada's negotiating team as they navigate the potentially rocky period ahead.

"It has been the greatest privilege of my professional life to have served and represented Canada and Canadians during this critical period in Canada-U.S. relations," she wrote.

"While there will never be a perfect time to leave, this is the right time to put a team in place that will see the [Canada-U.S.-Mexico Agreement] review through to its conclusion."

Hillman represented Canada in Washington as ambassador, first in an acting role and then formally as of 2020, and was the first woman to be appointed to the prestigious posting.

The lawyer helped the former Liberal government negotiate the updated North American trade agreement — now known north of the border as CUSMA. The agreement enters its mandatory review period next year.

She also served as chief negotiator for the Comprehensive and Progressive Agreement for Trans-Pacific Partnership.

Hillman pointed to her work helping secure the release of Michael Kovrig and Michael Spavor as a highlight. In 2018, the two Canadians were detained by China's communist regime for 1,019 days, collateral as part of an international legal dispute involving a Huawei executive.

"In a relationship as deep and complex as ours, pressing and consequential issues arise almost daily. Yet none was more personal to me than the hundreds of hours I spent with U.S. and Chinese counterparts working for the release of Michael Kovrig and Michael Spavor," Hillman wrote.

Prime Minister Mark Carney thanked Hillman for her intelligence and diplomacy.

"As one of the longest-serving ambassadors to the United States in our history, her wide-ranging and constructive engagement with all branches of the U.S. government as well as with leaders across America and Canada have yielded crucial results for Canadians," he said in a statement.

The prime minister did not indicate who he has in mind to take over her position.

Former prime minister Justin Trudeau called Hillman "a real patriot."

"Her skill, toughness and commitment to her country shone through from the very beginning," he wrote. "Kirsten, my dear friend, thank you for your outstanding service."