LONDON (Reuters) - Some Davis Cup ties will be reduced to a two-day format with best-of-three-set matches instead of best-of-five next year, the International Tennis Federation said on Friday.

Matches in the World Group will continue to be played over the long format for the time being, but could be changed depending on the outcome of an ITF trial for shortened ties in zonal group matches next February.

Two singles matches will be played on day one with the doubles, followed by two singles rubbers, on day two.

The ITF also announced that nations, including in the elite World Group, will be able to select from five players rather than four as part of a trial.

“We are as determined as ever to enhance our flagship team competitions for players, fans, host nations, broadcasters and sponsors,” ITF President David Haggerty said.

“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.”

The ITF announced in August that World Group matches would continue to be played over three days with best-of-five-set rubbers, after a proposal to shorten the contests failed to achieve the required mandate.

The team competition has suffered in recent years with top players unwilling to turn out for their countries owing to the crowded schedule and the timings of ties which mean they usually follow soon after grand slam tournaments.

“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,” Haggerty said.

“We are working to develop player-friendly formulas that give the competitions the profile and stature they deserve.”