India captain Virat Kohli is against the prospect of reducing Test matches to four days and fears it could eventually lead to debates over the future of the format. 

Four-day Tests are among the proposals the International Cricket Council is considering as they organise the international calendar for the period from 2023 until 2031.

Kohli is preparing his team for limited-overs matches against Sri Lanka, Australia and New Zealand this month.

But the 31-year-old, who has 27 Test centuries, took the opportunity to speak out against the proposed changes to the longest format of the game.

"I am not a fan," he told reporters about four-day Tests. "I think the intent will not be right because then you will speak of three-day Tests. 

"Where do you end? Then you will speak of Test cricket disappearing. I don't endorse that at all.

"I don't think that's fair to the purest format of the game, how cricket started initially. 

"Five-day Test matches was the highest you can have at the international level. According to me, it shouldn't be altered."

Optional four-day Tests and day-night matches in the longest format are already in operation. Kohli is more of a fan of the latter change, which he thinks boosts crowds and levels of interest.

"Day-night cricket is the most that should be changed about Test cricket, according to me," added Kohli, the world's number one batsman in Tests and ODIs.

"Then you're purely going to be talking about getting the numbers in and entertainment. I think it is very, very crucial to market Test cricket like we do for T20 and one-day cricket. 

"If there's enough buzz created around Test cricket, then there will be a lot more keenness to come to the stadiums.

"Day-night is another step towards commercialising Test cricket and creating excitement around it but it can't be tinkered with too much. I don't believe so."

Of other new formats, Kohli explained why he had steered clear of the England and Wales Cricket Board's new The Hundred competition.

He said: "T20 was a revelation in terms of introduction of a new format. 

"I was asked about the 100-ball format and I said I am not going to go and try myself out in another format because there's already so much going on."