Engineers drilling to reach 33 trapped miners in Chile say the men might be rescued as early as this weekend.
The head of one of the drilling operations, Pedro Buttazzoni, told the BBC his drill had only 160 metres further to go to reach the men.
Earlier, Chilean President Sebastian Pinera said rescuers were "very close" to getting them out.
The miners have been trapped underground for two months, longer than any previous group.
Mr Buttazzoni, the head of the Chilean mining company Geotec, said on Tuesday his drill had already cut through 464m of rock and his team expected to break through to the area where the miners are sheltering in 3 to 4 days.
He said rescuers were debating whether they would need to line the rescue tunnel with metal casing as planned, a process that would take several days.
If it was decided that the lining was not needed, it was "perfectly possible" that the miners could be brought to the surface by the weekend, he said.
Earlier, Mr Pinera said he hoped the miners would be rescued before his planned trip to Europe on 17 October.
Doctors say the miners have started exercising in preparation for using the specially made rescue capsule, in which they will be winched to the surface.
They are also getting training from public relations experts to help them cope with the attention of the world's media once they emerge.
The men were trapped by a rockfall at the mine near Copiapo, about 725km north of the Chilean capital Santiago, on 5 August. Rescuers had almost given up the search when they located the miners 17 days later.