HELSINKI — A landmark poll in Sweden reveals a massive shift in public opinion that favors the non-aligned Nordic state joining NATO. Conducted by research organization TNS Sifo (part of the WPP Group), the poll shows 41 percent support for Sweden becoming a full NATO member, 39 percent remain opposed and 20 percent are undecided.

"What is most surprising is the rapid change in opinion. Since the annexation of Crimea and crisis in Ukraine, we have seen a steady trend where opposition to NATO membership is in decline," said political analyst Ulf Bjereld.

The new figures represent a sharp 10 percent increase in pro-NATO support compared with a similar poll carried out in May. Swedish public support for joining NATO hovered at a lowly 17 percent in 2012. By year-end 2013 it was 29 percent.

The poll comes in the wake of an historic reversal in policy by the former NATO-skeptic opposition Center party.

Once staunchly anti-NATO membership, the Center is now advocating that Sweden join the Western alliance as part of a joint initiative with fellow non-aligned Nordic state Finland.

This simultaneous action, the Center contends, would help secure the long-term defense capabilities and national security interests of both nations in an increasingly unpredictable and potentially volatile region.

Three other opposition groups, the Liberals, Moderates and Christian Democrats, who together with the Center belong to the so-called alliance parties, also favor NATO membership.

This powerful political bloc is expected to pressure the ruling Social Democratic-Green government to test the nation's mood on NATO by convening a referendum.

"We are seeing a clear trend, and in particular alliance voters are moving toward a pro NATO membership position," said Toivo Sjörén, a public opinion analyst at TNS Sifo.

In contrast to rising pro-NATO support by alliance voters, supporters of the ruling Social Democrats and Green parties remain largely opposed to membership.

Around 52 percent of Social Democrat voters are against joining NATO while 30 percent support membership. Some 61 percent of Green voters oppose NATO membership while 27 percent favor joining.

In an interesting twist, the poll shows that while the leadership of the nationalist Sweden Democrats are opposed to NATO membership, 54 percent of the opposition party's supporters favor joining.

The poll results emerged several days after a delayed action by Sweden's Foreign Minister Margot Wallström to call in Russia's ambassador to Sweden, Viktor Tatarintsev, to explain controversial comments he made in July.

Tatarintsev warned that Russia's friendly relationship with Sweden would change markedly if the non-aligned state were to join NATO. Sweden, said Tatarintsev, would be subjected to "countermeasures" and would also run the risk of being targeted militarily.

"We are an independent state and it is Sweden that will make decisions about our security policies and our security policy choices. We do not think anyone should be threatening us, and I have contacted the Russian ambassador to ask some questions and give him the opportunity to explain matters," said Wallström.

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