UPDATE 2-Failed German nuclear restart sparks war of words

* Government divided over response

* Operator has no timeline for results of study, restart

(Adds Merkel, new Gabriel quote, latest from operator)

FRANKFURT, July 6 (Reuters) - The failed restart of an ageing German nuclear power plant on Monday sharpened the political battlelines within the coalition government, ahead of an election, on how quickly atomic power should be shut down.

Environment minister Sigmar Gabriel said Germany's policy of closing plants should move more quickly, after the Kruemmel reactor failed to complete a restart over the weekend and instead stopped working, causing power cuts.

Chancellor Angela Merkel via a spokesman rebuffed the minister, sticking to her demands of a more relaxed nuclear exit programme after the national election on Sept. 27.

Gabriel also said his party, the Social Democrats (SPD), will ensure that the exit programme will be tightened rather than relaxed, as is wished by the Conservatives (CDU), the SPD's stronger partners in the government.

He said Germany's eight oldest reactors should shut immediately and newer ones should not be allowed to operate longer.

"On September 27, Germans will decide whether this and seven other reactors can run longer, as Merkel ... wants, or if we can finally switch off ... eight of these difficult reactors," Gabriel told German television.

Vattenfall Europe's [VATN.UL] Kruemmel power station went off the grid at midday on Saturday when a transformer short-circuited after running at half load ahead of the botched full reopening.

This came after another transformer malfunction on Wednesday caused the go-slow, soon after the plant had restarted on June 28 in the wake of a two-year outage caused by a safety-related incident in the summer of 2007.

Kruemmel was built in 1984 and was meant to close in 2018 under a nuclear exit deal agreed in 2001, under which all 17 German reactors will close by 2021 at the latest.

The Conservatives want to allow longer running times, while stopping short of any new construction of nuclear plants.

Merkel believes nuclear is an important bridging energy before renewable energies become fully commercially viable and that decentralised supervision works successfully, deputy government spokesman Thomas Steg told reporters in Berlin.

Vattenfall on Sunday apologised for the problems, pledging an scrupulous investigation.

A Vattenfall spokeswoman said on Monday there was no time schedule for when results of the assessment would be publishable, nor for the likely restart of the plant.

"The analysis is underway," she said, adding the reopening "certainly would not be a matter of days."

Vattenfall had initially informed the police, not nuclear supervisors in the state of Schleswig Holstein where Kruemmel is situated, which prompted Gabriel to seize control.

Sector peer E.ON (EONGn.DE) owns 50 percent of Kruemmel but Vattenfall has always had the operational lead.

(Reporting by Vera Eckert and Thomas Krumenacker; Editing by William Hardy)