Rescuers on Tuesday began sending down emergency food, water and oxygen supplies to the miners trapped alive after the gold and copper mine collapsed on August 5.
The mine runs like a corkscrew for more than seven kilometres under a barren mountain in northern Chile's Atacama Desert.
"We were able to tell them... they would not be rescued before the Fiestas Patrias [Chile's September 18 Independence Day celebrations], and that we hoped to get them out before Christmas," Jaime Manalich, the Chilean health minister, said.
|The 33 miners will be stuck half a mile below the surface until the end of the year [EPA]
Manalich said the men, trapped 700 metres below ground, took the information calmly, but he warned "a period of depression, anguish and severe malaise" could ensue.
Sebastian Pinera, the Chilean president, earlier assured anxious families that their loved ones "will be with us for Christmas and New Year".
Rodrigo Hinzpeter, the Chilean interior minister, said the men have a general idea that the rescue will take time but have not been told how long they will remain stuck nearly half a mile below the surface.
"I hope that nobody commits the imprudence of telling them something like this. We have asked the families to be careful in the letters they write," Hinzpeter said.
"It's going to be very hard. We're going to have to give them a great deal of attention, care and psychological support."
On Tuesday the men made a desperate plea for early rescue.
"It was frightening. For about four or five hours, we couldn't see a thing. After that we saw that we were trapped by an enormous rock that filled the entire passage of the tunnel"
Luis Urzua, shift foreman
Luis Urzua, the group leader, told Pinera through an intercom cable to "rescue us as quickly as possible … and that you don't abandon us".
"Don't leave us alone. ... We hope that all of Chile shows its strength to help us get out of this hell," Urzua said.
The 54-year-old shift foreman also described the collapse.
"It was frightening. We felt like the mountain was coming down on us, without knowing what happened," he said.
Urzua said the "mountain came down on top of us" about 20 minutes before their scheduled lunch break.
"For about four or five hours, we couldn't see a thing. After that we saw that we were trapped by an enormous rock that filled the entire passage of the tunnel," he added.
Officials say they are concerned about the psychological impact of being trapped in close proximity in a hot, dank shelter with their only lifeline a tiny hole to the surface providing sustenance, water and communication.
|Families sent letters in an attempt to minimise the psychological impact on the men [AFP]
Family members holding a vigil on the surface used an eight-centimetre wide drill hole to the men to send written notes to buoy the men's spirits.
Health minister Manalich said the first stage of the preparation plan calls for the miners to receive "nutritional recuperation" and occupational therapy.
He said they had been sent chocolate- and raspberry-flavoured milkshakes, which would be followed by solid food in the coming days, when their metabolisms could cope.
The men have been told to split their living area for sleeping, working, and for bodily waste, with tiny lamps illuminating the cramped space.
"Then they will start a daily exercise routine," Manalich said. "The programme includes singing, games involving movement, card games, pencils and anything that they can use."
The US space agency NASA has also offered to help sustain the trapped men, based on its long experience with keeping astronauts healthy during long, isolated missions.