The children and the coach went missing on 23 June after venturing into the Tham Luang cave and being caught out by a flood caused by heavy rains.

Ten days later, they were found alive by a group of UK rescue divers. The rescue operation is currently underway with the divers supplying the boys and the coach with food, oxygen and medical attention.

"We hope that, in some way, our words of support may help bring them a little peace and courage in these difficult moments of uncertainty and concern. If, as we all hope, they are reunited with their families in the coming days and their health allows them to travel, FIFA would be delighted to invite them to attend the 2018 World Cup final in Moscow as our guests," FIFA President Gianni Infantino said in a letter to the Thai association.

Earlier on Friday, media reported that a former Thai navy seal, who was delivering oxygen to the boys and the coach, died in the cave after losing consciousness on his way back due to the lack of oxygen in his own tank.

Thailand's Navy Seal commander, Rear Admiral Apakorn Yookongkaew said on Thursday that the divers might have no choice but to try and get the boys out of the cave because heavy rains expected on Sunday threaten to flood the cave even further.