Former Canadian prime minister Brian Mulroney paid tribute to his “dear friend” Nancy Reagan, who died on Sunday, noting her “indispensable” support and devotion for her husband, former U.S. president Ronald Reagan.

The former first lady died on Sunday of congestive heart failure in her Los Angeles home at the age of 94. Her death came 12 years after her husband died in 2004, following a lengthy battle with Alzheimer's disease.

On Sunday, Mulroney issued a statement noting the close relationship he and his wife, Mila, had with her.

"Mila and I are deeply saddened by the passing of our dear friend, Nancy Reagan. But we are equally confident that she has been re-united with her beloved 'Ronnie,' and comforted that she lived such a full life, devoted not only to her husband but to the service of her country," he said in the statement.

Mulroney and Ronald Reagan both served in office during the 1980s, and forged a close relationship that often seemed to extend beyond the realm of politics. Mulroney's wife also became friends with the Reagans, and the two couples spent time together, hosting each other in Ottawa and Washington, D.C., and even taking holidays together.

Brian Mulroney

Mulroney said the Reagans served America with a "unique distinction," that was strengthened by their partnership.

"She was his indispensable partner in the White House, as she had been when he was Governor of California. As he was a great President, so she was a great First Lady," he said.

Nancy Reagan

The former prime minister said the Reagans were also "great friends" of Canada, recalling the many visits they shared.

He recalled one particular visit, when Reagan noted their common Irish roots – something that often came up during their time in power.

Nancy Reagan

"I will always remember our wives together at Ottawa Airport, and President Reagan saying to me: 'You know, Brian, for a couple of Irishmen, we sure married up,'" Mulroney said in the statement.

"Theirs was a great love story, and we cherish their memory and our friendship."

Nancy Reagan