UPDATE 1-Polish government to approve draft shale law next week

* Law keenly awaited by shale gas investors

* Publication postponed in past few months

* Firms including Chevron, Marathon hold licenses

(Adds background)

WARSAW, Oct 9 (Reuters) - Poland's government will approve a long-awaited new shale gas draft law next week, hoping to provide a stable legal environment for investors interested in exploring the reserves, Prime Minister Donald Tusk said on Tuesday.

Poland, which hopes tapping into previously inaccessible shale gas reserves will reduce its reliance on costly gas supplies from Russia, has postponed the publication of the law several times in the past few months.

"The assumptions are ready. We will be approving this draft at the government's sitting next week," Tusk said at a news conference.

The draft law will then need to be passed by parliament.

Tusk said the draft required striking a balance between ensuring state control and a fair distribution of the cash generated from shale gas, and keeping the rules liberal enough to attract private investors.

Piotr Wozniak, deputy environment minister responsible for the draft bill, said last week Poland wanted the law to go into force next year, but added that it would be best if a shale gas tax waited until at least 2016.

Poland relies on Russia's Gazprom for over half of the gas it consumes. Warsaw wants commercial production of shale gas to start as soon as possible so it can limit this dependence.

The shale gas law is eagerly awaited by companies holding shale gas exploration licences including Chevron and Marathon Oil , as well as Polish companies such as PGNiG

and PKN Orlen .

Poland granted 111 shale exploration licences even as other countries, including France and Bulgaria, halted shale exploration pending further environmental studies.

Poland had high hopes for shale after a study by the U.S. Energy Information Association in 2011 estimated Polish reserves at 5.3 trillion cubic metres, enough to cover domestic demand for some 300 years.

But estimated reserves were slashed to about a tenth of that in a government report published in March.

(Reporting by Maciej Onoszko; Editing by Alison Birrane)

((maciej.onoszko@thomsonreuters.com)(+48 22 653 97 11)(Reuters Messaging: maciej.onoszko.reuters.com@thomsonreuters.net))