BASF's Wintershall urges predictable Russian tax regime

* Gazprom's German partner remains keen on Siberian gas

* Calls for tax regime without big changes

* No comment on Russian report it exited existing deals

FRANKFURT, Oct 4 (Reuters) - The oil and gas arm of BASF

on Thursday said it needed a predictable tax regime to go ahead with new investments in Russia following a report it was deterred from a Russian project by higher taxes.

A spokesman for BASF's Kassel-based Wintershall unit did not comment directly on Wednesday's report by Interfax news agency that Russia's proposed increase in mineral extraction tax (MET) caused Wintershall's retreat.

He said Wintershall was interested in tapping more oil and gas reserves in geologically difficult parts of Russia and remained in "constructive talks" about expanding the cooperation in the Siberian Achimov region.

"A reliable tax regime that we can plan for could offer further incentives for investment," he said.

"It is important for long-term investors such as Wintershall that the tax policy and with it the tax system is reliable and not subject to big changes," he added.

Wintershall a year ago agreed with gas producer Gazprom a swap of stakes in its gas fields in the North Sea in return for more stakes in the Achimov layers of the Urengoy deposit in Siberia.

Last month, Russia's finance ministry proposed increasing the MET - albeit more slowly than previously suggested - by 12.5 percent for Gazprom and 15 percent for other producers starting from 2013.

Gazprom warned at the time it might be unable to take development decisions about strategic regions.

(Reporting by Frank Siebelt and Vera Eckert; Editing by David Cowell)

(( 69 7565 1228)(Reuters Messaging: