Speaking before an audience at the National Press Club, Trumka said that the administration could leave the "most oppressive pieces" of NAFTA in place despite President Donald Trump's harsh criticism of the 23-year-old trade deal with Mexico and Canada.

Trump called NAFTA a "disaster" throughout the 2016 election campaign, but the plan outlined in a draft notification letter would preserve many of its provisions, including a settlement system for other disputes that circumvents local courts.

The US Trade Representative's office circulated the letter with its NAFTA objectives to members of Congress for review. The letter, seen by Reuters, is part of the legal process required to start negotiations to revamp the NAFTA.

The AFL-CIO, an umbrella organization of unions representing 12.5 million workers, endorsed Trump's opponent in the presidential election, Hillary Clinton. But the AFL-CIO has long been critical of NAFTA and Trumka, the labor federation's president, met with Trump after the election.

Trumka said on Tuesday that the AFL-CIO will judge the Trump administration based on its actions and provide backing when it supports workers.

How Trump handles the revamping of NAFTA "will be the real test," Trumka said.

Trumka said there are dozens of changes to the trade pact that unions favor, such as making its labor standards fully enforceable and scrapping the entire dispute resolution system for antidumping and antisubsidy cases.