Wesley So, a grandmaster from Minnetonka, considers his next move while two rivals study the board during Round 6 of the U.S. Chess Championship at the Chess Club and Scholastic Center of St. Louis on April 4, 2017. Photo: Lennart Ootes, Chess Club and Scholastic Center of St. Louis (Mike Nelson — Chess Club and Scholastic Center of St. Louis/The Minnesota Star Tribune)

ST. LOUIS – Entering Saturday's penultimate round at the U.S. Chess Championship, Wesley So was in a two-way tie for first place.

Now the Minnetonka grandmaster finds himself with additional company — going into the final round on Sunday in a three-way tie for the lead.

So drew his game Saturday, as did his co-leader. Meanwhile, a third player caught up to them with a win in his own game.

The 23-year-old So is trying to win his first U.S. title, a national championship that is perhaps the toughest in the world because three American players, including So, are ranked among the top six in the world.

On Saturday, So played Grandmaster Gata Kamsky, a Soviet émigré and four-time U.S. champion. At 42, Kamsky is on the downside of his career but still capable of playing brilliantly — and of making "boneheaded clunkers," as Yasser Seirawan, a four-time U.S. champion, said before the round.

But Kamsky didn't falter, and by the end, he was the one posing serious threats. So had to calculate a queen and pawn ending, "which is the hardest thing you can do," said Grandmaster Maurice Ashley, providing live-stream commentary. But So didn't slip and after nearly 4½ hours, he and Kamsky agreed to a draw.

Meanwhile, So's co-leader, Grandmaster Varuzhan Akobian, drew his game to keep pace. And Grandmaster Alexander Onischuk won his game to jump from third place into a three-way tie for first.

So, ranked No. 2 in the world, entered the tournament as the top seed. Neither Onischuk, the No. 6 seed, nor Akobian, the 10th seed, were expected to be serious contenders.

This is So's third attempt to win the national title since he came to the U.S. from the Philippines on a college chess scholarship and then settled in Minnetonka.

In the final round, So will play Daniel Naroditsky, a 21-year-old grandmaster attending Stanford University. They've played three times and So said he has won each time.

"But that doesn't matter," So said. "Each game is different," and So will start at a slight disadvantage, having the black pieces.

The tournament ends Sunday; a tiebreaking playoff will be Monday if necessary.

Dennis J. McGrath • 612-673-4293