WASHINGTON, Jan 29 (Reuters) - U.S. President Donald Trump will ask Congress for a three-year-extension of the so-called “fast-track” trade negotiating authority before it expires July 1, Trump’s top trade official said on Monday.

“The president has made the decision, we’re going to ask for the extension of fast track authority. And we will get it,” U.S. Trade Representative Robert Lighthizer told reporters after the close of NAFTA talks in Montreal.

The extension is “pre-authorized” and would be automatic once Trump requests it unless either chamber of Congress passes a resolution to refuse it.

Lighthizer also said he would continue to discuss Canadian proposals to count automakers’ engineering, research and software content toward higher regional NAFTA autos content requirements, but dismissed the idea as creating too much opportunity to bring in more parts from China. (Reporting by David Lawder; Editing by David Gregorio)