REFILE-UPDATE 1-Golf-Mickelson suspends play, wife has cancer

* Mickelson withdraws from two tournaments in Dallas area

* Participation in next month's U.S. Open in doubt (Adds dropped words in eighth para)

LOS ANGELES, May 20 (Reuters) - Phil Mickelson has suspended playing on the PGA Tour indefinitely after his wife was diagnosed with cancer, officials said Wednesday.

The breast cancer in Amy Mickelson was discovered after an "extensive battery of tests," the golfer's manager T.R. Reinman said in a release.

More tests are scheduled but the treatment process is expected to begin with major surgery, perhaps within the next two weeks, Reinman said.

The couple married in 1996 and have three children aged nine, seven, and six.

Mickelson, 38, is a two-times Masters champion and winner of the 2005 PGA Championship.

The world number two was due to play the Byron Nelson Championship in Dallas beginning Thursday and defend his title at the Colonial Invitational in Fort Worth next week.

The situation casts doubt on Mickelson's participation in next month's U.S. Open at Bethpage in New York, where in 2002 the big left-hander finished second to Tiger Woods.