Teenager Ryan Harrison puts US up 4-0 on Swiss

FRIBOURG, Switzerland (AP) - Teenager Ryan Harrison made a winning Davis Cup debut for the United States on Sunday, beating Switzerland's Michael Lammer 7-6 (0), 7-6 (4) to extend the Americans' lead to 4-0 in their first-round series.

Harrison stepped up his play in the tiebreakers after showing an impressive all-around game to win in 2 hours, 14 minutes.

The 19-year-old right-hander was selected by captain Jim Courier after the U.S. sealed its victory Saturday, when Mardy Fish and Mike Bryan beat Olympic doubles champions Roger Federer and Stanislas Wawrinka.

Federer and Fish had been scheduled to play in Sunday's first singles match. The best-of-five series finishes with John Isner of the U.S. playing Marco Chuidinelli of Switzerland.