Laurence Golborne said drilling equipment was being changed in preparation for the final push, but he said it would be three to eight days before the rescue mission would begin.

Engineers said the shaft was now just 34m (112ft) from the chamber.

The miners were trapped 700m underground when part of the San Jose mine collapsed on August 5.

The miners have now been underground longer than any other group.

Andre Sougarret, the engineer in charge of the drilling, said the final part of the operation would have to be handled very carefully.