The big chess showdown between three-time defending champion Magnus Carlsen and his US challenger Fabiano Caruana will be decided by a series of rapid-play tiebreakers on Wednesday.

Norway’s Carlsen and Caruana wrapped up their 12-match World ChessChampionship series in London with their 12th successive draw on Monday.

It was an anti-climactic finish to a showdown between 27-year old Carlsen – a former child prodigy now regarded by many as the greatest ever chess player – and the first American contender to the crown since the legendary Bobby Fischer in 1972.

The result means the players will have a day off on Tuesday before getting together for an intense session of chess played in a completely different format.

They will try to settle things first in a four-game series in which each player will have 25 minutes. An extra 10 seconds of time are added for each move they make.

Things will go to an even faster-paced format if there is still no winner.

The final tiebreaker is a single winner-take-all game played in a lightning three minutes.

Carlsen will be viewed as the favourite on Wednesday. He excels at rapid chess and defended his title through tiebreakers against the Russian Sergey Karjakin in 2016.

“I think I have very good chances,” the Norwegian told reporters after Monday’s game.

But chess legend Garry Kasparov said he was losing faith in Carlsen.

The former Soviet and Russian world champion said Carlsen had the upper hand in Monday’s encounter but agreed to settle on a draw because he had lost his nerve.

“In light of this shocking draw offer from Magnus in a superior position with more time, I reconsider my evaluation of him being the favorite in rapids,” Kasparov tweeted.

“Tiebreaks require tremendous nerves and he seems to be losing his.”