The American pair of Zach Johnson and Phil Mickelson halved their match in Session 2 of the Presidents Cup golf competition after a bizarre ruling against Mickelson early in the round.

Playing the seventh hole Friday at the Jack Nicklaus Course in Incheon City, South Korea, Mickelson violated the "one-ball'' condition by putting into a play a different brand of ball. Rules stipulate players must play the entire round with the same brand and type (compression) of ball. Mickelson admitted he put a firmer ball in play to try and gain distance.

In addition, a rules official told Mickelson to pick up his ball on the seventh when in actuality he could have continued to play on. Johnson lost the hole to the team of Jason Day and Adam Scott and an additional penalty against Mickelson followed. The result was the Americans went from all square to 2-down in one hole.

Johnson birdied 18 with a short putt. Day followed with a 7-foot birdie to halve the match. The United States team holds a 5 1/2-4 1/2 lead going into Saturday's third and fourth sessions. Johnson and Mickelson were not scheduled to play the third session.

Johnson, a Cedar Rapids Regis product, teamed with Mickelson in the first session Thursday for a 2-up victory.

The American duo has drawn plenty of comment after they created an unusual way to celebrate their successes. Instead of fist bumps or high gives, Johnson and Mickelson merely face one another, shake hands and give a nod of their heads.

The Presidents Cup concludes Sunday with 12 singles matches.