Swedish Prime Minister Fredrik Reinfeldt put out feelers to traditional left-wing rivals as pressure mounted Tuesday to lock the far-right out of power after their dramatic electoral breakthrough.

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After his governing coalition appeared to have fallen just short of an outright majority in Sunday's legislative elections, the centre-right premier is having to make advances to what would be unlikely bedfellows.

But although Reinfeldt has so far met some resistance, there is pressure on all the mainstream parties to come to some kind of arrangement, with most attention focused on the Green Party.

"The responsibility for making it possible to govern Sweden today and in the coming term lies with the opposition as well," said an editorial in Dagens Nyheter, the country's leading daily.

"With a xenophobic party in parliament, there needs to be openness around negotiations across ideological lines. It needs to be possible to govern Sweden even though the government does not have a clear majority," the daily added.

Reinfeldt, whose centre-right coalition won most votes in Sunday's elections but is slated to fall three seats short of a majority in the Riksdag, has stressed he will not seek support from the far-right, anti-immigrant Sweden Democrats who entered parliament for the first time by winning 20 seats.

Reinfeldt has yet to make contact with the Greens, pointing out his bloc on Sunday was only about 7,000 votes from a winning a majority and he therefore wants to hold off negotiations until after votes from abroad have been tallied.

But the prime minister has already said he will seek support from the Greens, which soared in Sunday's vote to become Sweden's third largest party.

The Greens have in turn called on Reinfeldt to launch talks with all the leftwing parties to find a power-sharing solution.

Analysts say the Greens would have to make an ideological leap to link up with Reinfeldt's centre-right camp but predict some kind of deal will be forthcoming.

"It is not easy for a party like the Greens to switch sides," said Tommy Moeller, a political scientist at Stockholm University.

But Moeller added that he expects the party will opt to support Reinfeldt "if it looks necessary for the government to be able to govern effectively."

The prime minister meanwhile has hinted that, on some questions at least, he could consider cooperating with his main opponent Mona Sahlin's Social Democrats, who have dominated Swedish politics for 80 years and, despite a catastrophic election Sunday, remain Sweden's largest party.

"I can see several questions where the centre-right and Social Democrats traditionally agree," he told reporters Monday.

Experts say there is a theoretical possibility that the centre-right coalition could end up with a majority after the remaining 50,000 to 100,000 votes have been added to the result on Wednesday.

"The result so far is a bit disproportional. If the late votes land in a certain way, theoretically at least, the Social Democrats could lose three seats," said Svante Linusson, a mathematician at Stockholm's Royal Institute of Technology.

"It could happen. It's not impossible."

Moeller agreed: "The centre-right might actually have a majority," he said.

If the parliamentary balance does not shift, Moeller says the most likely scenario is "a minority government headed by Reinfeldt, who will need to seek support on different issues from different parties, including the Social Democrats and the Greens."

Moeller said such a scenario would not necessarily spell a weak and impotent government.

"We have a tradition of minority governments in Sweden," Moeller said.

He acknowledged that such a government would likely lose a number of votes in parliament, including on the issue of troops in Afghanistan.

"The goverment's authority could be weakened, but I don't think it will be forced to resign just because it loses a vote or two," he said.