By Terje Solsvik and Camilla Knudsen
OSLO (Reuters) - Five tiny political parties could all end up kingmakers in Norway's parliament after elections on Sept. 11, presenting a risk to Norway's key oil industry and making it even more difficult to form a government than before.
The Greens aiming to shut Norway's oil industry and the Marxist Red party seeking social justice are among those hoping for influence, as are the more experienced Socialist Left, centrist Liberals and the socially conservative Christian Democrats.
Overall, the Nordic nation faces at least ten potential alternatives for minority or majority coalition governments and the outcome of the vote is particularly hard to predict, pollsters say.
"Four years ago we had clearer blocks," election analyst Svein Tore Marthinsen told Reuters. "Today it is a little unclear what the alternatives on the left are ... and the picture is also unclear on the other side."
Polls show a dead heat between the center-right block of Conservative Prime Minister Erna Solberg and her rival, Labour leader Jonas Gahr Stoere - meaning the outcome could be decided by only minor changes to the support the small parties get.
While Solberg has pledged to cut income taxes to boost growth and jobs creation, Stoere seeks to hike taxes on high-earners and the wealthy to better fund Norway's extensive welfare state.
As western Europe's top oil and gas producer, the nation of some 5.3 million people has also amassed a sovereign wealth fund of close to a trillion dollars, and the next parliament faces key decisions over how risky investments it should make.
GREENS AND REDS
One poll on Wednesday showed that the right-wing government and its backers would win 81 seats while the center-left opposition could secure 77, leaving both sides short of an 85-seat majority.
The unaligned Greens would win 11 seats, the poll for financial daily DN showed, one of several surveys suggesting its vote could tip the scale.
Other polls suggest the Reds might become the decisive actor, however, or that the Christian Democrats, by switching allegiance away from the current government, could help Labour win power.
The Greens, who were credited with 6.1 percent of the vote in the DN poll, want to stop oil firms from exploring, which would limit the prospects of a sector that accounted for half of total exports last year.
"Our ultimatum, our single condition, is: 'Stop exploring for oil and gas'," Rasmus Hansson, one of the party's two national spokespeople, told reporters.
"We do it because of the climate and also because it is a key criterion of the Paris climate agreement."
The party, which also wants to shut Norway's petroleum output within 15 years, has declined to say if it will back Solberg or Stoere.
Both candidates have said the future of the Norwegian oil industry is crucial for them and that they would not be held hostage on this issue.
By contrast the Marxist Red Party, which was credited with 4.7 percent in an Aug. 15 poll, will back Labour's Stoere.
But its support comes at a price. It too seeks a phase-out of oil production and wants to introduce a six-hour working day, and renegotiate the agreement Oslo has with the EU for its access to the common market.
The Socialist Left is more moderate than the Reds and has governed with Labour before. But it also wants to scale back Norway's oil industry to fight climate change.
On the other side of the spectrum, the current governing coalition needs the continuing support of the Christian Democrats and the centrist Liberals in parliament.
But the Christian Democrats have become more reluctant to support a government that includes the populist Progress Party as they differ on immigration and asylum.
The Liberals, meanwhile, would prefer a government that does not include the Progress Party but could continue support the present coalition.
"It is very difficult to predict the outcome in any way," said Marthinsen.
For a graphic on Norway's parliamentary elections, click: http://tmsnrt.rs/2ugJCjo
(Additional reporting by Gwladys Fouche; Editing by Richard Balmforth)