The Thai governor in charge of rescuing 12 boys and their soccer coach from a cave says the co-operating weather and falling water levels over the past few days have created conditions for an attempted extraction of the group.
Narongsak Osatanakorn says authorities are waiting for two big groups of volunteer divers to arrive later on Saturday and Sunday, after which they will be ready to begin the operation of bringing the group out.
He said: "The plan that I've held on to from the beginning is that we have to bring the kids out and the determining factor of this plan is to have as little water as possible."
But he said while floodwaters have drained as much as possible, "if it rains and adds to it again, we don't know what other risk factors we will have to face". He also warned about higher carbon dioxide levels in the cave.
Meanwhile, the soccer coach trapped in the cave with his team has apologised to their parents in the first letter sent out with divers.
Ekapol Chanthawong, 25, the coach of the Wild Boars football team, wrote: "To the parents of all the kids, right now the kids are all fine, the crew are taking good care. I promise I will care for the kids as best as possible. I want to say thanks for all the support and I want to apologise to the parents."
The boys also wrote saying they are doing well and missing their families.
One wrote: "I'm doing fine, but the air is a little cold, but don't worry. Although, don't forget to set up my birthday party."
Another, identified as Tun, wrote: "Mom and Dad, please don't worry, I am fine. I've told Yod to get ready to take me out for fried chicken. With love."
The rest of the scribbled letters on pages from a notebook struck a similar message of love for parents and telling them not to worry.
A boy named Mick wrote: "Don't be worried, I miss everyone. Grandpa, Uncle, Mom, Dad and siblings, I love you all. I'm happy being here inside, the navy SEALS have taken good care. Love you all."
The boys and their coach have been trapped since June 23, when they went exploring in the cave after a soccer game.
Monsoon flooding cut off their escape and prevented rescuers from finding them for almost 10 days. The only way to reach them was by navigating dark, tight passageways filled with muddy water and strong currents, as well as oxygen-depleted air.
Rescuers are also pursuing other options to extract the boys, hoping that finding a shaft or drilling into the mountain in which the cave is located will lead them to a sort of backdoor entrance.