A decision timeline was unknown.
If approved, the first phase of the plan -- which involves the ongoing process of staging equipment and clearing obstacles in the cave -- could be completed by 6 p.m. local time Saturday. The second phase -- which calls for dangerous and risky “buddy diving” of the soccer team, in which they would each be accompanied by an experienced diver out of the cave network -- could start as early as Sunday morning local time.
U.S. dive and medical personnel will support the proposed operation by staging equipment and setting up triage stations, but will not go beyond the third chamber inside the cave, according to the document.
Narongsak Osatanakorn, the Thai official in immediate charge of the rescue operation, told reporters at a news conference late Friday that the plan was to bring the boys and their coach out of the cave the same way they initially entered two weeks ago. The group is currently learning how to breathe underwater using dive equipment, he said.
During a news conference Saturday morning, Narongsak said they would pull back some of the rescuers inside the cave in an effort to preserve oxygen levels.
"We have experienced a lot of people fainting inside," he told reporters. "We want to keep the headcount minimal, but we'll always have four people with the kids and we'll work hard to bring as many oxygen tanks into that area as we can."
The recent death of a former member of the Royal Thai Navy inside the cave who was working as a volunteer rescuer has hindered some progress that was already underway. Saman Gunan lost consciousness underwater during an overnight operation delivering extra air tanks inside the cave, along the treacherous route divers take to get to the trapped soccer team. He could not be revived and was confirmed dead early Friday morning.
Gunan, 38, formerly served in the Royal Thai Navy’s Underwater Demolition Assault Unit, colloquially known as the Thai Navy SEALs. His death marked the first fatality in the operation to rescue the group and underscored the dangers of navigating through the cave underwater, even for those who have experience.
A planned operation to potentially “buddy dive” the group out of the cave, which the United States was going to support by pre-positioning air tanks in the seventh chamber, was cancelled due to the Gunan’s death and the associated risks, according to the internal U.S. government report.
"We will learn from our mistakes and try not to repeat them again," Narongsak told reporters Saturday. "I will have to use the word 'try' here because I cannot make a commitment that something like this won't happen again. We can only use the words 'try' and 'do our best.'"
A plan to install an oxygen cable in the chamber also had to be abandoned due to difficulties in routing the cable through the cave’s labyrinth of caverns and narrow passageways.
In the meantime, crews continued drilling into the south side of the cave complex on Friday to reduce the water level. It’s estimated to take an additional 12 to 18 hours to penetrate approximately 200 meters of rock. Drilling on the north side was suspended, as engineers and geologists work to find an alternate location closer to the stranded group.
According to the document, pumping operations have not been able to significantly lower the water level deep within the cave network. Rescue crews have assessed that the ongoing effort to pump water out from the main entrance of the cave has reached a point where it’s becoming less and less effective, and placing pumps further inside the cave -- beyond the 800 meter mark, where they currently are -- does not seem possible.
Medical assessments indicated the trapped children have good oxygen levels, with all of them having oxygen saturation levels of 95 percent and above. The oxygen level within the cave was most recently measured at 17.5 percent. Though higher than the previous reading, it is still significantly below the normal range of 20 to 21.5 percent.
Rescue crews have also determined that it’s impractical to bring into the cave the necessary amounts of food and supplies that are required to sustain the boys and their coach before the oxygen levels drop to fatal levels or the water level rises. Divers can only bring in small amounts of supplies at a time.
The U.S. Embassy and the Royal Thai Navy continue to receive offers from Xylem and Elon Musk to provide technical support in the operation. Both Xylem and Musk plan to send engineering experts to be integrated with the proposed operation Saturday.
The boys, ages 11 to 16, and their 25-year-old soccer coach have been trapped inside Tham Luang Nang Non, Thailand’s longest cave, since June 23. It’s believed the coach often took the Wild Boar teammates to the cave in Khun Nam Nang Non Forest Park for fun excursions after practice.
But as the group ventured deeper into the cave that Saturday afternoon, the sky opened up and it began to rain. The downpour sent floodwater rushing into the mouth of the cave and cut off their exit route. The group forged ahead until finding a dry, raised slope where they’ve remained stranded.
After they didn’t return from their hike, Thai officials launched a massive search and rescue operation involving more than 1,000 people, including specialists drafted from various nations such as Australia, China, Japan, the United Kingdom and the United States. On July 2, two British divers found all 13 alive in an area about three miles from the cave’s main entrance.
A team of Royal Thai Navy members, a doctor and a nurse have been staying with the group ever since, giving them high-powered protein drinks and medical assessments, while officials work on a plan to get them out as safely and quickly as possible.
During a press conference early Friday morning, Thai Navy SEAL commander Rear Adm. Arpakorn Yookongkaew said there is “limited amount of time” to rescue the group.
"We can no longer wait for all conditions [to be ready] because circumstances are pressuring us," he told reporters. "We originally thought the boys can stay safe inside the cave for quite some time but circumstances have changed."
ABC News' Brandon Baur, Joohee Cho, Matt Gutman, Aicha El Hammar, James Longman, Luis Martinez, Matt McGarry, Scott Shulman and Robert Zepeda contributed to this report.