WASHINGTON (AFP) - US President Donald Trump on Monday called for "reciprocal" trade with Canada and to build bridges of commerce across the border, appearing to tone down previously harsh rhetoric on trade.

"America is deeply fortunate to have a neighbor like Canada," Trump told a joint press conference with visiting Canadian Prime Minister Justin Trudeau at his side, hailing the opportunity to "build even more bridges" of commerce.

"We understand that both of our countries are stronger when we join forces in matters of international commerce," Trump said.

For his part, Trudeau said the two nations - who with Mexico make up the North American Free Trade Agreement - "will always remain each other's most essential partner." "Today's conversations have served to reinforce how important that is for both Canadians and Americans," said Trudeau.

Throughout his campaign and since his November election, the new Republican president has voiced his determination to put "America first" and rip up NAFTA, which he has said is a "catastrophe" for American jobs.

The economic ties between America and its northern neighbor, who share the world's longest common border, run deep: three-quarters of Canada's exports go to the US, and Canada is the top destination for exports from about 30 US states.

Renegotiating NAFTA will not be simple and Trudeau, a fervent supporter of free trade, has emphasized the importance of the tripartite pact for his country's economy and warned against protectionism.

Trump has not been specific on how he wants the negotiations to develop.

"When we sit down as we did today and as our teams will be doing in the weeks and months to come, we will be talking about how we can continue to create good jobs for our citizens on both sides of the border," Trudeau said.

Trump added: "We have a very outstanding trade relationship with Canada. We will be tweaking it. We will be doing certain things that are going to benefit both of our countries."