Chile's mining minister says a shaft wide enough to rescue 33 miners should reach the men by Saturday.
Laurence Golborne said that once the drill breaks through, it could take anywhere from three to ten more days to pull the miners to safety.
The countdown cannot begin until engineers they determine whether to insert a steel sleeve in the shaft.
That could reduce the risk of something going wrong on the miners' way up, but lowering the pipe through curved sections of the shaft could also be risky.
Expectations have been high amongst the families that a rescue is only a matter of days away, after the country's president said this week that his government was close to pulling the trapped miners to safety.
Sebastian Pinera said he hoped to be there in person to see the rescue before leaving on a trip to Europe on October 17.
