Matildas captain Kerr has a record 77 regular-season goals in her NWSL career and is the league's three-time Golden Boot winner, but she had never scored in her three previous playoff games.

The Matildas' star striker took just eight minutes in Sunday's game in Chicago to erase that anomaly with a right foot shot from the right side of the box into the bottom left corner of the goal.

The goal came from a superb pass from Japanese star Yuki Nagasato.

"She puts the ball on a platter and I don't have to do much," said Kerr.

The win ended the Red Stars' luckless record in the playoffs, having been knocked out in four consecutive semi-finals and it was the first time since 2013 they beat Portland.

Portland attempted to spark their offence by inserting Matildas star Hayley Raso from the bench after the half-time break and the forward did cause Chicago trouble.

The Thorns also feature Matildas Ellie Carpenter and Caitlin Foord while Chicago's reserve goalkeeper is Australian Mackenzie Arnold.

The Red Stars will now face North Carolina Courage in the title decider next weekend.

The Courage made the final after a 4-1 win against the Seattle Reign, who feature Australians Steph Catley and Lydia Williams.

The teams were locked 1-1 at the end of regulation in North Carolina on Sunday but the Courage stormed home in extra time to win 4-1 and book a place in next weekend's championship game.

Australian Associated Press