OSLO (Reuters) - Norwegians vote on Sept. 10 and 11 to pick a parliament for the next four years and determine whether the center-right minority government stays in power or is replaced by parties on the center-left. Opinion polls show the election remains too close to call. Exit polls and forecasts based on early votes will be made public on Monday at 1900 GMT, and most ballots will be counted within three to four hours. In the case of an exceptionally tight race however, the final result may not emerge until late on Tuesday. Below is a summary of key policy differences and the dynamics of the race: All 169 seats in parliament are up for grabs, and as many as nine parties are expected to win seats under Norway s system of proportional representation. However, there are only two candidates for the job of prime minister - the incumbent Erna Solberg of the Conservatives and Labour s Jonas Gahr Stoere. A calculation by www.pollofpolls.no, measuring the average of September opinion polls, gave Solberg s four-party block 85 seats, just enough for a majority, while the four on the center-left, plus the independent Green Party, would win 84 seats. But whether it s the center-left or center-right that hits the crucial 85 seats, the winner faces tricky post-election negotiations and will meet tough demands from small parties to keep their support over the next four years. The race could be decided by how many of the small parties clear the key four-percent hurdle that gives access to a pool of so-called  seats at large , boosting their presence in parliament. Two parties on the right, two on the left and one in the center, the Greens, are all close to this key threshold. Solberg seeks further cuts in personal income tax and a reduction of the wealth tax, but has declined to say by how much. She requires backing from the centrist Liberals and Christian Democrats, which would temper the size of any cuts. Labour has vowed to raise taxes for above-average earners and the wealthy by up to $2 billion to improve public services and reduce the reliance on cash from Norway s sovereign wealth fund. Citing concerns over climate change and potential pollution, several small parties seek to limit the expansion of Norway s oil and gas industry, which brings in almost half the country s export revenues. The independent Greens, which could hold the balance of power in post-election maneuvers, have made it a condition for anyone seeking their support to end all exploration   a demand that neither Labour nor the Conservatives are willing to meet. Meanwhile, the Liberal Party hopes to slow down the awards of new exploration acreage to oil firms if the Conservatives stay in power, while on the left the Reds and the Socialist Left will make similar demands of a Labour-led government. The seas surrounding the arctic Lofoten archipelago could thus remain off-limits to the oil industry, while the extent of drilling in the far-north Barents Sea may emerge as a flash-point in post-election negotiations. With nearly $1 trillion saved up from Norway s extensive oil and gas industry, the next parliament faces key questions over how to organize the fund and whether to allow investments beyond the foreign stocks, bonds and real estate it currently holds. Decisions are mostly made in consensus between the bigger parties, however, and neither Labour nor the Conservatives have said whether they agree with a recent report that suggested it should no longer be managed by the central bank. If Labour s Gahr Stoere emerges as the likely next prime minister, he will face pressure from center-left parties to review EU-outsider Norway s extensive inclusion in the European Union s single market. At stake is Norway s participation in the European Economic Area (EEA) treaty, strongly favored by both Labour and the Conservatives but opposed by the euro-skeptic Centre Party (CP) and the Socialist Left (SL). However, both the CP and the SL, in government with Labour from 2005 to 2013, agreed at the time to govern on the basis of the EEA. An interactive Reuters graphic of polling data can be found at tmsnrt.rs/2wYkVIO 
Factbox: Norway's close-fought election for parliament