The International Cricket Council (ICC) has given the green light to a Test championship and one-day international league, while countries are also welcome to experiment with four-day tests, the world governing body said on Friday.

A Test championship has long been mooted as a means to make the longest form of the game more relevant for fans who have increasingly turned towards limited-overs matches.

ICC Chief Executive Dave Richardson told reporters in Auckland on Friday that while details still needed to be worked out, the test championship would commence after the 50-overs World Cup in 2019 and culminate with a final in June 2021.

Nine of the 12 test-approved countries -- Zimbabwe, Afghanistan and Ireland will initially be excluded -- will play three home and three away series over the two years that count towards the championship.

The series can be a minimum of two matches and maximum of five, with all tests to be five days in length. The top-two teams in April 2021 will meet in a 'World Test League Championship Final'.

According to cricket.com.au, every Test series will have the same number of points on offer regardless of how many matches are played in the series, though the points system is yet to be finalised.

The ODI league, set to begin in May 2020 will feature 12 full Test playing nations plus the winner of the current ICC Cricket League Championship, cricket.com.au further added.

In the first edition of the ODI league, each team will play four home and four away series. Each series will comprise of three ODIs and the league will provide direct qualification to the 2023 World Cup in India.

"The approval of both leagues is the conclusion of two years of work from the members who have explored a whole range of options to bring context to every game," ICC chief Richardson said.

"The ICC Board decision means we can now go and finalise a playing schedule ... as well as the points system, hosting arrangements and competition terms."

Richardson said countries were welcome to experiment with four-day test matches but they would not count towards the championship.

South Africa will play Zimbabwe in cricket's first four-day test on Dec. 26 and Richardson said that while the concept was still in the trial phase it should help Afghanistan and Ireland, who were granted test status in June, get up to speed faster.

"Throughout the discussions about the future of test cricket it became clear that whilst context is crucial we must also consider alternatives and trial initiatives that may support the future viability of test cricket," Richardson said.

"The trial is exactly that, a trial, just in the same way day-night tests and technology have been trialled.

"Four-day tests will also provide the new test-playing countries with more opportunities to play the longer version of the game against more experienced opponents, which, in turn, will help them to hone their skills and close the gap with the top nine ranked teams."