Four British cave experts, including Rick Stanton and John Volanthen who found the 12 Thai schoolboys and their coach five days ago, are expected to lead a rescue mission in what is being described as a “buddy dive” in the coming days.

However, Chiang Rai Provincial Governor Narongsak Osottanakorn told  reporters just before midnight on Friday (local time), the boys were “not ready to dive” and their rescue was not imminent.

He said rescue plans were dependent on the boys, aged between 11 and 16, being taught basic scuba-diving skills to navigate the treacherous cave network, and working on regaining their strength.

The rescue bid, according to ABC America, Thai navy SEALS and expert divers from the US are currently briefing local authorities and the military on a two-phase plan before forecast heavy rains in the coming days.

Oxygen levels remain steady and, if the plan is approved, the first phase could be completed by 6pm (local time), involving the ongoing process of staging equipment and clearing obstacles in the cave.

The second phase, according to ABC America, which calls for dangerous “buddy diving” out of the cave chambers – could start as early as Sunday morning local time.

The biggest fear is heavy rain forecast for the next three days: “If it rains heavily, they will try and bring them out,” he said, before confirming there will be no rescue attempt on Saturday.

But after two weeks trapped two kilometres below surface in the Tham Luang cave complex, nine days of those without food, the strength of the schoolboys and their soccer coach is flagging.

“The boys’ (condition) are not suitable … (they) cannot dive at this time,” Mr Narongsak told reporters, Channel News Asia reported.

“We’d like minimum risk. But we can’t wait until it rains heavily and worsens the situation. If that happens, we’ll need to reassess. The key thing is the kids’ readiness to dive.”

Chiang Rai governor says they are preparing to rescue trapped boys and will do so if heavy rain comes. They have got a pipe to carry oxygen in so air quality no longer a worry. But rain could make rescue harder and staying untenable. Could happen this weekend.

— Jonathan Head (@pakhead) July 6, 2018

Oxygen is being pumped into the cave, buying rescuers more time, but torrential rain forecast in the coming days will make the operation more difficult and could lead to flooding inside the cave complex, forcing authorities to make an early rescue.

The second option of drilling a one kilometre shaft into the cave is being explored but is considered too time-consuming, especially given the monsoon rain forecast.

British divers emerged from the caves at 9pm (local time) and said the boys were relatively fine. Handwritten letters from their family members were delivered to the boys by the divers on Friday.

Their coach, a former Buddhist monk, has filled the dark hours with words of encouragement, of hope and meditation lessons to get his young charges’ minds off their predicament and deadly peril.

But reports from the scene say the coach, the only adult in the group, is fading – weak from hunger after giving his meagre rations to the boys and worn down by the cold and efforts to maintain morale.

Wrapped in heat-conserving space blankets delivered by the heroic divers who found them in the flooded labyrinth, the boys’ prospects have ridden a roller-coaster of hope and despair.

Thai schoolchildren offers their prayers for the soccer boys’ rescue as hope fades.

Everything seemed possible when divers returned to the surface with news that the boys were alive and relatively well on Monday, nine days after they went missing.

Having been written off as likely dead days earlier, it seemed at that moment their rescue was only a matter of time and patience.

That was then, but the monsoonal weather, which broke early and trapped them in the first place, would have none of it.

“The pressure we are experiencing comes from working against the weather, as the forecasts tell us there will be heavy rain in this area within 48 hours,” Thai SEAL commander Arpakorn Yookongkaew, one of the rescue leaders, said.

The rain started on Friday and the best predictions say it will continue to bucket down.

“Yes, we are pumping out the water as fast as we can, but it flows in even faster,” one of the weary would-be rescuers told CNN.

With the cavern system largely unmapped, hand-drawn guides are all rescuers have to work with. Map: ABC 

The longer and harder it comes down, the more problematic the various rescue scenarios become – a grim fact reinforced by the death of a former SEAL and volunteer diver who perished for lack of oxygen on his way to the boys.

While dive team leaders debate how to get the children out and whether to risk leading each one on the four-kilometre journey to safety, they are excruciatingly aware that the lowest dips in the tunnel are filling with water.

Sections that would have required only a short underwater swim are said to be growing longer by the hour. Even under perfect conditions such an extraction would have been a nightmare, now it is far, far worse than that.

Rescuers manhandle additional pumps to the cave, but water levels keep rising.

Meanwhile, the world watches and prays – and rescue leaders’ prayers are the most fervent of all. No matter which option they consider, none is good.

“I have asked the doctor and the SEAL team who are working on the rescue operation to assess the situation and see what risk level we can take,” Chiang Rai Provincial Governor Narongsak Osottanakorn said.  He has ordered 13 sets of dive gear be readied for immediate use.

“For example, if we can accept the 90 per cent safety level, and if all conditions are at that 90 per cent, then we are ready to bring them out. And that’s what we are prepared for.”

As the rains continue to come, that “90 per cent safety level” is shrinking – and even apparent good news doesn’t withstand scrutiny.

On Thursday, for example, reports emerged that the boys were hearing the sound of dogs and chickens, which seemed to suggest that there might be another unknown and unimpeded route to the surface.

Hopes soared – only to be dashed when experts noted that aural hallucinations and group hysteria would be natural byproducts of such an extended time in the dark.

Neveretheless, even though they represent the slimmest of slim hopes, professional cliff climbers, who normally collect birds nests for exotic soups, were recruited to see if they could find an alternate route to the boys and their chaperone.

Officials concede it is a long-shot hope, but as the rain falls that is all there is.

That, and prayer.