Prominent Republican Rick Santorum says he was stunned when Prime Minister Justin Trudeau pre-emptively offered to sit down with U.S. officials to discuss the North American Free Trade Agreement.

Santorum, who ran against U.S. president-elect Donald Trump for the Republican presidential nomination, said Canada has already failed to butt out the new administration's smouldering distaste for the agreement that created the world's biggest free-trade zone.

In an interview with Evan Solomon, host of CTV's Question Period, Santorum said a negotiator who speaks first during a stare-off usually loses the negotiation.

"I was stunned," said Santorum, who eventually supported Trump's presidential bid and is considered to be close to him. "I think it was not a good move for you guys, great move for the United States."

"And I'm not too sure he was going to ask for anything.... When [Trump] was talking about NAFTA, I guarantee you he wasn't thinking Canadian workers and Canadian trade."

The interview will air Sunday morning on CTV.

During the campaign, Trump frothed up simmering anger over NAFTA, promising to rip it up if he isn't satisfied it can be renegotiated to the benefit of the U.S. But the U.S. trade relationships with Canada and Mexico are far from analogous, Santorum suggested.

"What he's really looking to renegotiate is Mexico, where we have a huge trade deficit, where they've devalued the peso, where they have all sorts of issues at the border that come into it," Santorum said.

The spat with Mexico could present an opportunity for Canada if the Canadian government plays its cards "smart," he added.

"I'm not too sure your prime minister actually came out of the gate in a very good position by willingly agreeing to negotiate."

When it comes to Trudeau's burgeoning relationship with Trump, Santorum said, "he's 0-for-1 so far."

Watch CTV's Question Period on Sunday mornings at 11 a.m. ET, 10 a.m. CT, 9 a.m. MT and 8 a.m. PT.