Democrats in Congress have reached a deal with the White House to approve a new North American trade pact before the end of the year.
House Speaker Nancy Pelosi said the new agreement would have tougher labour and environmental rules.
She declared it “infinitely better” than the deal the White House reached with Mexico and Canada last year.
US President Donald Trump, who had made the deal a priority, also declared victory.
The pact will be “the best and most important trade deal ever made by the USA. Good for everybody – Farmers, Manufacturers, Energy, Union – tremendous support,” he tweeted.
The US-Mexico-Canada Agreement (USMCA) is set to replace the North American Free Trade Agreement (Nafta), which Mr Trump and Democrats have blamed for speeding the decline of US manufacturing.
Negotiators from the US, Mexico and Canada had reached a deal last year, but it needed to be approved by lawmakers in the three countries to move forward.
Democrats in the US were pushing for stronger mechanisms to enforce labour and environmental rules, as well as more flexibility governing drug pricing.
“There is no question, of course, that this trade agreement is much better than Nafta but… it is infinitely better than what was initially proposed by the administration,” Ms Pelosi said.
Mexico’s President, Andres Manuel Lopez Obrador, said representatives would sign an amended pact in Mexico on Tuesday.
The US business community said news that the deal with two of America’s biggest trade partners would move forward was a relief and urged Congress to bring it to a vote quickly.
“Farmers have been struggling in the face of bad weather and unpredictable trade policy,” said Angela Hofmann, co-executive director of the lobby group, Farmers for Free Trade.
“Passing USMCA will guarantee that our farmers’ closest and most important markets, will remain free from tariffs and red tape.”