The United States will lose its credibility in the Asia-Pacific region if Congress does not ratify the Trans-Pacific Partnership trade pact by the end of the year, a former senior U.S. trade official said.

The new U.S. president will be sworn in on Jan. 20.

"If you ask me what this means without TPP, it's really a loss of credibility for the U.S. in the region. And that really troubles me," Wendy Cutler, former acting deputy U.S. trade representative, said in an interview in Tokyo on Thursday.