Michael Chang completed a dramatic comeback from two sets down to beat Horst Skoff and give the United States a 3-2 victory over Austria in their Davis Cup semifinal today.

Chang, who was trailing two sets to one when darkness halted play Sunday, overcame Skoff today 3-6, 6-7 (4-7), 6-4, 6-4, 6-3.The victory propelled the United States into the Davis Cup final against Australia Nov. 30-Dec. 2 in Florida. It is the first time the United States has reached the final since 1984, when it lost to Sweden 4-1.

Nationally . . .