INDIAN WELLS, California, Nov 14 - Russian teenager Mirra Andreeva extended her unbeaten run at the WTA Finals on Saturday, beating American Jessica Pegula 6-3 6-4 to reach the final of the season-ending tournament.

Andreeva's heavy groundstrokes, strong serving and tireless defense were too much for Pegula in their first career meeting, played under sunny skies in the California desert.

"It was a tough match," Andreeva said. "You have to work hard to win a point against her. She is going to leave everything out there and make your life complicated, so I wanted to make her life complicated as well today."

The opening set was tight until Andreeva pounced on a looping Pegula shot and hit a forehand winner to break for a 5-3 lead.

Pegula, backed by a supportive crowd, earned break points as Andreeva served for the set. She shanked an overhead long, however, and Andreeva took the set two points later when Pegula's backhand found the net.

Pegula broke early in the second set to lead 3-1 after Andreeva sent a backhand long. The third seed broke straight back with a deft volley and broke again to lead 4-3 before sealing the win when a Pegula backhand sailed long.

Andreeva, making her WTA Finals debut, has not dropped a set in four matches at the event.

She will face either sixth seed Elina Svitolina or eighth seed Linda Noskova in Sunday's final. The $10 million tournament was moved from Riyadh to the Indian Wells Tennis Garden because of the US-Israeli war with Iran. REUTERS