The Trump administration will deliver a letter to Congress on Thursday, notifying lawmakers of the White House's intent to renegotiate NAFTA, three sources familiar with the matter told CNBC.
The letter, which Commerce Secretary Wilbur Ross has said he's been waiting for, would open a 90-day window for the U.S. to get its negotiating strategy together.
Delivering the letter Thursday would put the end of the 90-day window in mid-August, at which time the U.S. can begin talks with Mexico and Canada on how to modernize the North American Free Trade Agreement.
Ross hinted on "Squawk Box" that the letter was going to come soon. "I think it's imminent, and I certainly hope so because we've been waiting a long time for it. I could happen anytime now."
NAFTA was negotiated in the early 1990s by Republican President George H.W. Bush and signed into law in 1993 and implemented during Democrat Bill Clinton's presidency.
The latest apparent movement on NAFTA comes after Robert Lighthizer was sworn in Monday as U.S. trade representative. He's since been meeting with small congressional groups on what they want to see in a NAFTA renegotiation.
Lighthizer on Thursday is going to Vietnam to meet with Asia-Pacific Economic Cooperation trade ministers.
The White House did not respond to a request for comment.
— CNBC's Kayla Tausche contributed reporting