The plight of 12 Thai boys and their coach from the "Wild Boar" football team has transfixed Thailand since they became trapped in a cramped chamber of the Tham Luang cave complex on June 23.
Rescuers have conceded that evacuating the boys is a race against time with monsoon rains expected to undo days of round-the-clock drainage of the deluged cave.
"Now and in the next three or four days, the conditions are perfect (for evacuation) in terms of the water, the weather and the boys' health," Narongsak Osottanakorn the chief of the rescue operation told reporters.
"We have to make a clear decision on what we can do."
While the oxygen level had stabilised he warned levels of "carbon dioxide are another factor" in considering when to move the group -- in addition to impending rains which could cover much of the muddy ledge on which the group are sheltering.
"The water level may rise to the area where the children are sitting and make the area less than 10 square meters," he said, citing estimates from cave divers and experts.
In the early hours of Saturday morning he said the boys were not yet ready to dive-out of the cave, a complex and dangerous task through twisting and jagged submerged passageways.
But his comments 12 hours later suggest the thinking has changed, with water levels inside the cave currently managed to their lowest point by constant drainage.
Earlier on Saturday Thai Navy SEALS published touching notes scrawled by the trapped footballers to their families, who are waiting for them agonisingly close-by outside the cave entrance.
The children urged relatives "not to worry" and asked eating their favourite food once they are safely evacuated.
In one Pheerapat, nicknamed "Night", whose 16th birthday the group were celebrating in the cave when they became stuck on June 23 said:
"I love you, Dad, Mum and my sister. You don't need to be worried about me."
Meanwhile the 25-year-old Ekkapol Chantawong coach, the only adult to accompany the boys into the cave, sent his "apologies" to their parents.
"To all the parents, all the kids are still fine. I promise to take the very best care of the kids," he said in a note given to divers on Friday. "Thank you for all the moral support and I apologise to the parents."
The boys are being trained in the basics of diving in case the floodwaters force authorities into a sudden evacuation.
- 'Limited time' -
The risks were underlined by the death on Friday of a former Thai Navy SEAL diver, who ran out of oxygen while returning from the chamber where the boys are trapped.
Saman Kunan had been trying to establish an air line to the chamber when he passed out and perished.
"We lost one man, but we still have faith to carry out our work," Navy Seal commander Apakorn Yookongkaew said, adding that rescuers have "a limited time" to extract the boys.
Ekkapol's message is the first from the coach, whose role in the team's predicament has split Thai social media.
Many have lauding him after reports he gave his share of food to the kids before they were located and helped them get through nine days in the darkness.
Others have criticised him for agreeing to take the young boys into the cave during the monsoon season. The group entered the cave on June 23 and got trapped as floodwaters gushed in.//AFP