Minnetonka chess Grandmaster Wesley So made a move against 16-year-old Grandmaster Jeffery Xiong in their game Friday at the U.S. Chess Championship in St. Louis. (The Minnesota Star Tribune)

ST. LOUIS – With just two rounds left in the U.S. Chess Championship, Minnetonka Grandmaster Wesley So is tied for the lead, with a third player only a half-step behind — setting up a homestretch scramble for the national title.

So, the No. 2-ranked player in the world, won his ninth-round game Friday in spectacular fashion, delivering a game that experts were calling one of the best in U.S. Chess Championship history.

With the victory, So extended his unbeaten streak to a remarkable 65 games dating to last July, one of the longest such streaks in history among elite players.

"It's a big relief," So said after the game. "It's a much-needed win, and it gives me a big boost."

So, 23, came into the tournament as the hottest player on the planet. He had won each of the last three international "super tournaments" he played in and was a double gold-medal winner at the Chess Olympiad last September in Baku, Azerbaijan.

Although the U.S. Championship, held at the Chess Club and Scholastic Center of St. Louis, is restricted to the top 12 U.S. players, it has become perhaps the toughest of national championships because the United States has three players ranked among the top six in the world.

Since his win in the first round on March 29, So has either held a share of the lead or been the sole leader. But his wins have been hard to come by. He had only two wins to go with six draws before Friday's victory.

But in Friday's game against a 16-year-old wunderkind from Texas, Grandmaster Jeffery Xiong, So returned to winning form, delivering what the grandmasters doing live-stream analysis of the tournament called a masterpiece. So first crashed through with a knight sacrifice to expose Xiong's king to attack, and then finished off the game with a queen sacrifice that left Xiong with nothing to do but resign.

"We are not worthy," four-time U.S. Champion Yasser Seirawan said as he complimented So after the game.

"That's why a lot of people play chess, because of [beautiful] games like this," said Jennifer Shahade, a two-time U.S. women's champion.

As So finished his game, it looked like his co-leader, Grandmaster Varuzhan Akobian, was about to lose his game against the reigning U.S. champion, Fabiano Caruana. But Akobian staged a stunning comeback to win and keep pace with So.

Players get one point for a win and a half point for a draw. So and Akobian each have six points, and Grandmaster Alexander Onischuk has 5.5 points.

In other words, with two rounds still to play there's plenty of time for a shakeout among those three.

The final two rounds are Saturday and Sunday, unless a playoff is needed to break a tie for first place, which carries a $50,000 prize. The playoff would be on Monday.

Dennis J. McGrath • 612-673-4293