According to ESPNcricinfo, the "ideas are included in a discussion document which details radical suggestions for change" in the domestic and international game.
They form part of a wide-ranging review into the future of English cricket, both domestically and internationally. Such changes, if proposed, would have to undergo an extensive discussion process within the ICC if they were eventually to be adopted.
Reduction in the five-day format would mean deviating from a tradition that has been there for more than 30 years. Tests have routinely been played over five days since 1979, an exception being when India met West Indies over six days in Kanpur.
The document includes a section suggesting the new president of the England and Wales Cricket Board - the former chairman, Giles Clarke - can use his influence at the ICC to bring change.
Clarke remains the ECB's representative at the ICC and is believed to retain ambitions of one day chairing the organisation. India, England and Australia also now have widespread powers to run the international game much as they see fit.