ST. LOUIS – With just two games left in the tournament to determine the U.S. chess champion, Minnetonka's Wesley So remains undefeated, but his chances of winning the title slipped slightly on Saturday.

So began Saturday's round tied for the lead, but when So drew with his opponent and the tournament co-leader won his game, that left So a half-step behind in his quest for the national championship.

Playing with the black pieces against the youngest contestant in the elite 12-player field — 15-year-old Jeffery Xiong from Texas — So chose a safe variation that often leads to draws, rather than gambling with a riskier line that could end in a loss.

Both grandmasters had studied the time-tested moves so deeply ahead of time that they blitzed out their moves, and with neither player able to gain an advantage, they agreed to a draw hours before many of the other games finished.

"A draw is better than a loss," So said, expressing mixed emotions after the ninth round at the Chess Club and Scholastic Center of St. Louis.

So is now alone in second place, only a half point behind sole leader Fabiano Caruana, who has 7 points. Two other players are a half point behind So. Players get 1 point for a win and half a point for a draw, so with the top four players bunched so closely and with two games left to play the championship remains up for grabs.

"My chances here are still very unclear," So summed up.

Caruana agreed. "I still think anything can happen," he said.

This is So's second attempt at the U.S. championship, and his four wins and five draws so far have elevated him in the world rankings. At one point during the tournament, the 22-year-old rose from 10th place to seventh best in the world. After Saturday's draw, he was ranked as the world No. 9.

One benefit of his quick draw Saturday is that it left So with extra time to prepare for his final two opponents. Of the two, Sunday's is likely to be his toughest. He'll be paired against Ray Robson, his former college roommate at Webster University in suburban St. Louis, which the Filipino-born So attended before quitting college in 2014 to become a chess professional and moving to Minnetonka. Robson has been lurking just behind So and Caruana in the standings all tournament.

So's other plans for the extra time on his hands after his quick draw? Get some extra sleep.

The tournament ends Monday, and the winner collects $50,000.

Dennis J. McGrath • 612-673-4293