SEOUL, South Korea — The human Go champion said he was left “speechless” after his second straight loss to Google’s Go-playing machine on Thursday in a highly-anticipated human versus machine faceoff.

Lee Sedol, 33, one of the best Go players in the world with 18 world championships, was ashen after the game, which lasted more than four hours.

“I’m quite speechless,” he said at the news conference that was livestreamed on YouTube. “It was a clear loss on my part. From the beginning there was no moment I thought I was leading.”

The latest victory by AlphaGo over South Korea’s Lee puts Google’s AlphaGo team one victory away from claiming the $1 million prize.

If AlphaGo wins, the prize money is to be donated to UNICEF, Go organizations and charities.

AlphaGo’s first win against Lee, on Wednesday, shook the Go-playing world, marking a milestone in the development of artificial intelligence.

Many had believed it would take another decade for computers to conquer the ancient Chinese board game, one of the most creative games ever devised and the only board game left to conquer after chess was mastered by computers in 1997. Go is much more complex than chess.

Google’s team compared AlphaGo’s win to landing on the moon.