TOKYO (AFP) - Mongolian grand champion Hakuho secured an unassailable lead Friday in the summer sumo tournament, denying a rival Bulgarian vying to be the first European to take the top rank.

Hakuho, 23, enjoyed a clean sweep of victories and no losses on the 13th day of the 15-day tournament in the central city of Nagoya, ensuring he will win his seventh career title.

The 192-centimetre (six-foot-four), 156-kilogram (344-pound) Mongolian drove veteran Japanese wrestler Kaio out of the ring using the frontal force-out technique.

The tournament was a disappointment for Kotooshu, a Bulgarian who had hoped for a strong showing to elevate him to the top rank of "yokozuna" or grand champion.

Kotooshu, real name Kaloyan Mahlyanov, put on a mediocre performance, losing four times during the tournament.

The Bulgarian stormed through the last tournament in May, becoming the first European to claim a tournament trophy.

Only two wrestlers currently hold the title of yokozuna -- Hakuho and fellow Mongolian Asashoryu.

Asashoryu, the fifth-ranked wrestler in modern sumo history, pulled out of the Nagoya tournament after a weak start, citing injuries. Asashoryu is said to need at least three weeks of treatment for a damaged elbow.

Hakuho has enjoyed a warmer reception in Japan than his compatriot Asashoryu, who has struggled to win over a sumo establishment that has accused him of being too abrasive for the ritual-heavy sport.

Besides Asashoryu and Hakuho, only two foreigners, both Americans from Hawaii, have reached the title of yokozuna in the 2,000-year-old sport.

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