by Andy Schooler
Two-day Davis Cup ties, with best-of-three-set matches, will be trialled in the Davis Cup in 2018 - but the elite World Group will remain unchanged.
Only the lower levels of the tournament will be subject to the trial, which has been introduced by the International Tennis Federation.
At its AGM in August, the ITF board controversially won the right to make trial changes to the competition after member nations had rejected a proposal to bring in best-of-three matches.
The two-day format in the zonal, lower divisions of the competition will see two singles matches played on day one, with the doubles contest followed by the two reverse singles rubbers taking place on day two.
In another shake-up, team size is to be increased from four to five players "to give nations greater flexibility in team selection". This rule will apply in the World Group.
The ITF is aiming to make the competition more attractive to the top players, many of whom have opted not to compete in recent years. Andy Murray, Roger Federer and Rafael Nadal all failed to play a tie in 2017.
ITF president David Haggerty (pictured) said: “We are as determined as ever to enhance our flagship team competitions for players, fans, host nations, broadcasters and sponsors. The nations voted to give the board the flexibility to trial changes, and the board has acted quickly to make this happen in 2018.
"The board felt it was appropriate to trial the two-day, best-of-three-set format at Zone Group level. Should the trial prove to be a success, we will be in a position to consider whether it should be applied for the World Group as well after 2018."
He added: "Our priority remains to attract the top players, and these trials address some of the challenges that these players face in an increasingly crowded tennis calendar. We are working to develop player-friendly formulas that give the competitions the profile and stature they deserve.”
The ITF has also floated the idea of staging the Davis Cup final at a neutral venue but that will not happen until 2019 at the earliest as talks over the proposal continue.
The Davis Cup has come under pressure with new team competition the Laver Cup, which saw a European team face 'Team World', having recently received a good reception after it did manage to attract many of the game's top names.
The ATP, who run the main men's tour, is also in discussions about creating a 'World Cup of tennis' to add to its schedule.
France will host Belgium in this year's final next month. France are Sky Bet's 2/9 favourites with Belgium the 100/30 outsiders.
Great Britain's next tie will be in the first round of the World Group in February when they head to Spain.