FILE PHOTO: Tesla Chief Executive Office Elon Musk speaks at his company's factory in Fremont, California, U.S., June 22, 2012. REUTERS/Noah Berger/File Photo

NEW YORK (Reuters) - A company owned by Elon Musk that is trying to lower the cost of building high-speed transit tunnels is nearing completion on the first tunnel, Musk said on Twitter on Sunday.

The first tunnel, under Hawthorne in the Los Angeles area, is almost done and will open on Dec. 10, Musk said. Privately held Boring Co has been promoting its plans for tunnels that would allow high-speed travel between cities.