(Adds Canadian prime minister rejecting idea of quotas on metals exports)
By David Ljunggren
OTTAWA, April 4 (Reuters) - Canadian Foreign Minister Chrystia Freeland on Thursday cautioned against the idea of reopening a new continental trade pact with the United States and Mexico, saying it could be a "Pandora's box."
U.S. House Speaker Nancy Pelosi told Politico this week that changes needed to be made to the text of the United States-Mexico-Canada (USMCA) trade deal to ensure its labor provisions could be enforced.
"When it comes to the issue of actually opening up the agreement, that's where Canada's view is, we've done our deal," Freeland told reporters on the sidelines of a NATO meeting in Washington when asked about Pelosi's comments.
"This was a very intense negotiation. A lot of time, a lot of effort went into it, compromises were made on all sides, and we believe that people need to be very careful around opening up what could really be a Pandora's box," she added.
One part of the deal - which was signed last November after 15 months of sometimes rancorous negotiations - was a chapter designed to boost labor standards and wages in Mexico.
Democratic lawmakers say the pact must ensure workers in Mexico have the right to organize, a step that would require new Mexican labor laws.
"Canada has done its share, we have done our work, and now it's up to each country to work on ratification," said Freeland.
She reiterated that Canada could find it hard to press ahead with efforts to ratify the treaty as long as U.S. maintained tariffs on imports of Canadians steel and aluminum.
Canada has campaigned hard for the removal of the punitive measures, which the Trump administration unveiled last May, citing national security.
U.S. officials have suggested the tariffs could be scrapped if Canada agreed to quotas on exports of steel and aluminum, an idea that Ottawa rejects.
"We are saying that will not happen. We do not want to limit the growth of that industry," Canadian Prime Minister Justin Trudeau told reporters in Alma, Quebec. (Reporting by David Ljunggren; editing by Dan Grebler and G Crosse)
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