By Christoph Steitz and Andreas Rinke

FRANKFURT (Reuters) -The German government plans to take a 30% stake in Uniper and will allow the utility to pass on some energy costs to customers as part of a bailout package that sources told Reuters could be finalised this week.

The government also plans to quadruple a credit line to the company via state-owned bank KfW, lifting it to 8 billion euros ($8.2 billion) from 2 billion euros, according to an economy ministry document seen by Reuters.

Reuters earlier reported that Berlin was leaning towards taking a stake of up to 30% and that a deal would allow Uniper to pass on soaring prices to customers.

Germany is scrambling to rescue Uniper, which has become a high-profile casualty of an economic standoff between the West and Russia. That standoff has sent gas prices soaring and raised fears of severe energy shortages this winter.

"To cover the accumulated losses, a combination of a capital increase with a target federal investment of 30% in Uniper and additional hybrid equity is planned," the document said.

It was not immediately clear by how much Uniper might be allowed to pass on costs under the rescue deal or what measures the German government could take to shield vulnerable households from a steep price increase.

Chancellor Olaf Scholz's government is grappling with how to share out the bailout costs. It is in talks with Uniper parent Fortum, majority owned by the Finnish state, which does not want Fortum to contribute more equity.

Uniper declined to comment. A German government spokesperson said Germany was working urgently on a solution but declined to give further detail. The Finnish government did not immediately respond to a request for comment.

"Stabilising Uniper secures gas supply. In doing so, we are looking for ways to keep price increases for consumers as low as possible," said Ingrid Nestle, climate protection and energy spokesperson for the Greens, which are part of the government coalition.

"However, it is also clear that we cannot define away the eightfold increase in purchase prices for gas."

Shares in Uniper were up 12% at the top of Germany's mid-cap index on Wednesday.

DEADLINE LOOMS

Details of the bailout are still being discussed and could be addressed at a meeting with Scholz on Friday, two people familiar with the negotiations said.

No final deal has been agreed and details could change as talks between the German and the Finnish governments, Uniper and Fortum continue, the sources said.

A rescue package must be agreed by July 25, when the German utility could face more serious funding issues as a result of reduced gas supplies from Russia, the sources added.