Sergei Balyasnikov said that 1.5 meters of new glacier core have already been extracted and the main aim is to extract 50 more meters of the core before work is suspended on January 25.
The majority of the core will be left in Antarctica, with the remaining samples sent to Russian scientific laboratories and to a laboratory in France.
Scientists plan to resume drilling work during the Antarctic summer in 2006-2007 and to reach the lake itself in 2007-2008.
The research work at Lake Vostok is being conducted under a Federal program named The World Ocean, involving scientists and specialists from nine Russian science and research institutes.
Lake Vostok is the largest of more than 70 lakes lying beneath the thick Antarctic ice sheet. The pristine waters of Lake Vostok have been isolated by a shield of ice some 3km thick for millions of years.
The subglacial environment represents one of the most oligotrophic environments on Earth, with high oxygen content but low plant nutrient levels.
If life thrives in the environments it may have to depend on alternative energy sources and survival strategies, scientists have suggested.