Pique was in the Spanish capital on Monday and Tuesday this week with negotiations ongoing on when and where such a tournament could fit into the packed tennis schedule.
The plans would see the whole tournament take place in one location over a maximum of 10 days.
"I think that it's a really exciting idea. If it comes off, I think it would be a very, very good thing for tennis," said Murray after his defeat to Borna Coric at the Madrid Masters on Thursday.
"Tennis needs an event like that, and I think it would be very good."
Such a tournament could spell more problems for the much-criticised Davis Cup, which currently has three-day matches spread over February, April, September and November.
As a result many of the sport's biggest stars have turned their back on the competition in order to prioritise preparations for Grand Slams
"For many years they have been static," Nadal said of the Davis Cup organisers the International Tennis Federation.
"They haven't moved with the times or looked for new solutions."
"Pique is part of a group that wants to create a World Cup that would be a great and very interesting tournament to compete in.
"It would be a fantastic initiative if it goes through and hopefully it will."
Djokovic also backed the plans after saying he had met personally with Pique "several times."
"The schedule is quite complicated, but I'm really glad that there are people like Gerard that are willing to invest the time and energy to make this game better," said the Serb.
"Hopefully it's going to come to life."