Prime Minister Justin Trudeau had a conversation with U.S. President Donald Trump on the sidelines of the NATO summit in Brussels Wednesday.

During the unofficial bilateral meeting, the pair discussed trade, including NAFTA, the Prime Minister's Office said without elaborating further. Trudeau and Trump also discussed the new Mexican President Andres Manuel Lopez Obrador.

An official described the closed-door conversation as “positive,” The Canadian Press reported.

The NATO summit is the first time Trudeau and Trump have been face-to-face since Canada levelled retaliatory tariffs on U.S. goods, over its steel and aluminum tariffs on Canada.

It was also their first in-person meeting since the G7 which ended in acrimony and was followed by Trump and members of his administration levelling personal attacks at Trudeau, including Trump calling the prime minister "very dishonest and weak" in a tweet. Trump’s blunt criticism came after Trudeau said Canada won’t be “pushed around” by the U.S. on trade.

Despite the recent flare-ups, the two leaders avoided a public confrontation Wednesday. During a photo-op, Trudeau stood to the side as Trump chatted with other leaders, including Britain's Theresa May and NATO Secretary General Jens Stoltenberg.

Instead, Trump directed his ire at German Chancellor Angela Merkel, accusing her country of being “totally controlled” and “captive to Russia” because Germany has a pipeline deal with its easterly neighbour.

Merkel responded by insisting that Germany makes its own policies and decisions.

Trump levelled a more general broadside at NATO allies, accusing them once again of not meeting defence spending commitments. Trump suggested ally countries spend four per cent of their GDP on defence, which is double the existing NATO goal of two per cent by 2024.

The U.S. itself does not meet the four per cent mark. According to the Pentagon, the U.S. spends 3.3 per cent of its GDP on defense. 

The Trudeau government has vowed to increase defence spending by 70 per cent over the next 10 years. Even after that investment, Canada would still fall short of the goal and only reach 1.4 per cent by the deadline.

Ahead of the NATO meeting, Trump sent a letter to Ottawa expressing “growing frustration” about the shortfall.

Trudeau downplayed the importance of the defence spending goal on Tuesday, calling it a “limited tool” to gauge a country’s NATO commitment.

The summit ends Thursday after a final day of meetings.