Police stand guard outside the Tham Luang cave complex after Thailand's government instructed members of the media to move out urgently, in the northern province of Chiang Rai, Thailand, July 8, 2018.
He said Dr Harris had all the characteristics to undertake the rescue mission.
Around 1,000 people are involved in the complex rescue operation.
Narongsak Osottanakorn, a former provincial governor leading the effort said the "ideal time" for a rescue could come in the next two or three days.
Fairfax says water levels in the first 600 metres of the cave remained stable overnight, despite heavy rain.
"Today we are at peak readiness", Mr Osottanakorn said.
"We are ready. The boys are ready and strong enough to come out". "We originally thought the boys can stay safe inside the cave for quite some time, but circumstances have changed".
"We hope for nothing but the best outcome for the trapped children, their families, and the global team involved in the rescue operations, and would like to thank the many members who have offered suggestions or volunteered to assist".
The operation has begun to rescue 12 boys and their football coach who will need to dive out of the flooded Thailand cave where they have been trapped for more than two weeks, with officials saying Sunday morning that "today is D-Day", the Associated Press said.
The letters make for remarkable reading. "Please tell Yod to take me out to a fried chicken shop", one boy said.
Don't worry about me too much. Grandpa, uncle, mum, dad, and siblings I love you all.
Professional cave divers from Europe are making the risky dives with a contingent of Thai navy SEALs. "Night loves you all".
Another, Tan, wrote: "Mum and Dad don't worry about me, I'm fine".
Another joked: "Teacher, don't give us lots of homework!"
Thai officials had been leaning in their public statements toward a quick underwater evacuation because of fear that access to the cave could soon close again because of seasonal monsoon rains expected this weekend.
Federation Internationale de Football Association president Gianni Infantino has written to the Thai FA to invite the 12 boys and their coach trapped in a cave to the World Cup final.
"To all the parents, all the kids are still fine".
"The SEAL team takes very good care of us", wrote Panumat "Mix" Saengdee, 14. "I want to say thanks for all the support and I want to apologise to the parents".
He said he wanted to reduce risks but added that falling oxygen levels inside the cave were another "really big concern".
Mr Chongklai Worapongsathorn, deputy director-general of the Department of National Park, Wildlife and Plant Conservation, said many holes have been drilled and many teams have been sent out to look for more, but so far, none of them can lead to where the boys are.
Authorities continue to pursue a third option, which is finding a shaft or drilling into the mountain in which the cave is located to find a sort of back door entrance.
The group was found to be skinny, but in good health, and have received high-protein drinks as they are treated by the Underwater Demolition Assault Unit.
The rescue effort suffered a disheartening setback Friday with the death of a former Thai navy SEAL diving in the flooded passageways to deliver supplies, as authorities raced against worsening weather and lessening oxygen.