Toronto: Teenaged Indian Grandmaster D Gukesh shot into sole lead after defeating Firouzja Alireza of France in the 13th and penultimate round of Candidates Chess tournament here, his quest for the extraordinary placing him on the cusp of becoming the youngest ever World Championship contender.
If the 17-year-old from Chennai emerges victorious at the Candidates, he will take on China's Ding Liren for the world champion's crown.
In the women's event, Humpy Koneru drew with Anna Muzychuk while Vaishali Rameshbabu got the better of Lei Tingjie. The 22-year-old Vaishali has now registered four consecutive wins in her last four games.
Needing a win to go ahead after the other overnight leaders, Russian Ian Nepomniachtchi and American Hikaru Nakamura played out a quick draw, Gukesh was awarded for his perseverance as he capitalised on a late blunder by Alireza in a difficult situation.
Gukesh took his tally to 8.5 points out of a possible 13 to emerge half-a-point ahead of Nepomniachtchi, Nakamura and Fabiano Caruana of the United States.
R Praggnanandhaa and Vidit Gujrathi share the fifth spot on six points apiece with Firouzja on 4.5 and Abasov has 3.5 points.
Of the three players in pursuit, Caruana defeated Praggnanandhaa in a hard-fought game while Gujrathi could only get a draw with Nijat Abasov of Azerbaijan.
Gukesh will next meet Nakamura who plays white in the last round game and Caurana will have the advantage of the favourable colour against Nepomniachtchi.
While anyone among the four players can win the event, the odds are hugely in favour of Gukesh as the pundits believe that a draw might just be enough for him.
In the women's section, Zhongyi Tan took a one point lead over nearest rival and compatriot Tingjie Lei following a draw with top seed Russian Aleksandra Goryachkina.
Vaishali spoiled the party for Lei by scoring a fine victory while Koneru Humpy and Nurgyul Salimova of Bulgaria drew with Anna Muzychuk of Ukraine and Kateryna Lagno of Russia respectively.
Just a draw away from clinching the crown, Lei is in second spot on 7.5 points. Goryachkina, Lagno, Humpy and Vaishali are on 6.5 points, sharing the third spot as Salimova and Muzychuk share the seventh spot with five points apiece.
Results (round 13) (Indians unless specified): Women: Zhongyi Tan (Chn, 8.5) drew with Aleksandra Goryachkina (Fid, 6.5); Koneru Humpy (6.5) drew with Anna Muzychuk (5); R Vaishali (6.5) beat Tingjie Lei (Chn, 7.5); Nurgyuaal Salimova (Bul, 5) drew with Kateryna Lagno (Fid, 6.5).
Men: Vidit Gujrathi (5) vs Nijat Abasov (Aze, 3); D Gukesh (7.5) vs Firouza Alireza (Fra, 4.5); R Praggnanandhaa (6) vs Fabiano Caruana (USA, 7); Ian Nepomniachthi (Fid, 7.5) vs Hikaru Nakamura (USA, 7.5).
