First four trapped boys saved from Thai cave

"CONDITIONS MUST BE STABLE"

"If we wait and the rain comes in the next few days we will be tired again from pumping and our readiness would drop. If that's the case, then we have to reassess the situation," he said.

"We can only carry on the operation once we are ready and this will be done soon, because the air tank and other systems have to be reinstalled," he told reporters later.

"...I can't give you an exact number but it should be more than 10 hours but not exceeding 20 hours. The conditions must be stable like today before we can continue the operation."

An Australian doctor checked the health of the boys on Saturday night and gave the all-clear for the operation to proceed.