The Americans will meet Spain in the championship game Sunday, a rematch of the title contest in Beijing four years ago. On that occasion Team USA delivered a 118-107 gold medal win after holding only a 2-point lead midway through the fourth quarter.
Spain reached the gold medal game by overcoming a halftime deficit to defeat Russia 67-50.
The United States had a 7-point lead at the break over Argentina, a team it defeated 126-97 in group play.
Durant then got hot from the outside on his way to scoring 19 points and by the end of the third period the American lead had grown to 17.
Carmelo Anthony and LeBron James both added 18 points for the United States, which shot 53 percent from the field. The Americans attempted more shots from outside the 3-point line (42) than they did from inside it (39).
Manu Ginobili paced Argentina with 18 points.
Jose Calderon hit two 3-pointers in a 14-1 fourth-quarter run to key the Spanish victory over Russia.
The Russians limited Spain to 20 points in the first half and appeared on their way to a second victory of these Olympics over the 2008 silver medal winners.
Spain then warmed up from 3-point range to overcome a 9-point deficit and tied it through three quarters, only to fall behind again by 3 with 9:13 remaining in the game.
Over the next 5 minutes the Russians could score only 1 point while Spain was storming to a 60-50 lead.
The Spanish made just 2-of-11 3-point tries in the first half and then hit 7-of-12 over the final two quarters.
When the teams met in group play early in the Olympics, Russia overcame a big early deficit to down Spain 77-74. Russia went 5-0 to win its group and then defeated Lithuania in the quarterfinals.