The world’s top Go player, Ke Jie, still believes he is the one to beat AlphaGo, the artificial intelligence program that just thrashed South Korean grandmaster Lee Sedol, but admits his chance of winning dwindles fast as his opponent self-improves at a stunning pace.

Developed by Google’s London-based AI subsidiary DeepMind, AlphaGo on Tuesday ended a historic match of the ancient Chinese board game with Lee by clinching the final match to win the best-of-five series 4-1 over 7 days.

Ke, the youngest player with three world titles, who had claimed “AlphaGo can’t beat me” before the much-hyped contest, kept up his confidence.

“I believe I can beat it. Machines can be very strong in many aspects but still have loopholes in certain calculations,” said the 18-year-old.

But the Chinese player was aware that his winning chance will become slimmer as time goes by due to AlphaGo’s super strong learning ability.

“It can teach itself and evolves better and better. It is hard to predict (who is going to win) after some time,” he said.

A few days earlier, Ke put his winning ratio at 60 percent.

It has been eagerly anticipated, at least in China and by DeepMind developers, that Ke takes on AlphaGo in the next Man vs Machines Go contest.

DeepMind CEO Demis Hassabis had expressed interest in inviting Ke as AlphaGo’s next opponent and company research scientist Raia Hadsell made the challenge directly.

“Up for a match, Ke Jie?” she said on her Facebook page after AlphaGo won a ranking in human Go Ratings, a 4th place 3,533 points following its defeat to Lee on Sunday. AlphaGo’s rating climbed to second yesterday.

Ke, currently world No. 1 in Go Ratings, defeated Qiu Jun, a ninth dan, to win the 2nd Bailing Cup final, and became the new world champion on January 14, 2015 when he was just at the level of fourth dan.

Then Ke, having already acquired Go’s highest level of ninth dan, won the 2015 Samsung Cup by defeating Shi Yue on December 9 in Shanghai, becoming the first player to win two major international titles in a single year since Lee’s feat in 2011.

Ke was born in 1997 and became a pro in 2008. His performance wasn’t especially notable until 2013, and he became a very strong player in 2014.

Go is a complex ancient Chinese board game. The two contestants move black and white stones with the aim of seizing the most territory.