ROME -- Prime Minister Justin Trudeau is standing by the Kinder Morgan pipeline project, even as the New Democrats and Greens in B.C. are teaming up to fight it.

"The decision we took on the Trans Mountain pipeline was based on facts and evidence on what is in the best interests of Canadians and indeed, all of Canada," Trudeau said Tuesday in Rome at a joint news conference with Italian Prime Minister Paolo Gentiloni.

"Regardless of the change in government in British Columbia or anywhere, the facts and evidence do not change."

The Liberal government understands that growing a strong economy requires taking leadership on both the environment and the economy, he added.

"That is what drives us in the choices we make. We stand by those choices."

Trudeau's comments followed Monday's news that B.C.'s anti-pipeline Green party and the provincial NDP have come to an agreement that could see the formation of a minority NDP government in the province, casting doubt on the project's future.

Both parties have voiced their opposition to the Trans Mountain expansion, which would nearly triple the capacity of the pipeline that runs from Edmonton to Burnaby, B.C.

For Alberta Premier Rachel Notley, the pipeline stand of the West Coast New Democrats threatens a project that she says is vital both to her province and the national economy. No province can veto the line, she said in a statement.

"It's important to note that provinces do not have the right to unilaterally stop projects such as Trans Mountain that have earned the federal government's approval," Notley said.

"This is a foundational principle that binds our country together. There are no legal tools available to provinces to stand in the way of infrastructure projects that benefit all Canadians."

Kinder Morgan went ahead Tuesday with its initial public offering for the expansion. Shortly after the opening bell, shares (TSX:KML) traded at $15.77, down 7.24 per cent from the $17 they were priced at in their initial public offering. The first trade was for $16.25.

Trudeau also praised the benefits that international trade can bring to a world where people are anxious about the future, holding up the trade deal between Canada and the European Union as an example of creating new jobs and ensure more people can benefit from economic growth.

"We are proud of it, and you should be, too," he told 45 parliamentarians and other dignitaries in the Sala della Regina, or the Queen's Room, a majestic committee room at the Chamber of Deputies in the Italian Parliament.

"It will create the kind of growth that benefits all our citizens, not just our wealthiest."

The trade agreement, known as CETA, is now being considered by the Senate.

Trudeau thanked the Italian parliamentarians who supported the deal, and said it would not have been possible without the support of "like-minded" leaders like Gentiloni.

International Trade Minister Francois-Philippe Champagne said the Liberal government hopes to bring other countries onside with trade by promoting it alongside Canadian values.

"There's enormous interest for what Canada stands for," he said. "The progressive and inclusive trade agenda is what, obviously, is the highlight, but we're really building the bridges."

Champagne also said Trudeau had given him the job of making trade "real" for people, by highlighting the tangible benefits for consumers.

"The best way to convince those who may not yet be convinced is to show them the real benefits."

Trudeau is in Italy to promote trade and cultural ties between the two countries at the end of a trip to Europe that included the NATO meeting in Brussels, the G7 summit in Sicily and a private audience with Pope Francis at the Vatican.

The coded language about working together and sharing values follows U.S. President Donald Trump's refusal to support the G7 consensus among the other six leaders, including Trudeau, to commit to the Paris agreement on climate change.

Trudeau was asked whether he shares the views expressed recently by campaigning German Chancellor Angela Merkel, who has said it is time to think about whether Europe can rely on the U.S. and other longtime allies.

Trudeau stepped gingerly with his response.

"We will always work together and highlight the shared values that are equally important on both sides of the Atlantic, including in the United States," Trudeau said.

"The way we can work on that together, where we have discussions, where we agree, is going to continue to be based in openness, frankness, robust exchanges, and in the conviction -- with regards to climate change particularly -- that the only way to move forward is to protect the environment while creating the jobs that we need for today and tomorrow."

On Tuesday, Trudeau was introduced with glowing remarks by Laura Boldrini, president of the Chamber of Deputies, noting his efforts at fighting climate change. "The biggest challenges can't be tackled alone," she said in Italian.

Pietro Grasso, president of the Senate, expressed concern over the "isolationism and protectionist sentiment" that was heard at the G7 summit.

Trudeau addressed the anxiety that people around the world are facing as "the twin forces of technology and globalization" change everything, and quickly. Those same forces can be harnessed to develop solutions to problems like climate change, he noted.

"Leaders who think we can hide from these changes, or turn back the clock, are wrong," he said. "It's our responsibility to harness these changes and make them work for people."