Japan's Prime Minister Shinzo Abe
Japan's Prime Minister Shinzo Abe, in the country for the Asia Pacific Economic Cooperation (APEC) forum, gestures as he talks to the media at a news conference in Beijing on Nov. 11, 2014. Reuters/Petar Kujundzic

(Reuters) - Prime Minister Shinzo Abe dissolved parliament's lower house on Friday for a snap election on Dec. 14, seeking a fresh mandate for his struggling "Abenomics" revival strategy just two years after he returned to power promising that "Japan is Back."

Abe had vowed to revive the economy with a mix of hyper-easy monetary policy, government spending and reforms, while moving ahead with plans to rein in Japan's massive public debt.

But doubts have grown about his strategy, especially after data showed this week that the economy had surprisingly slipped into recession in the third quarter after an initial rise in the sales tax to 8 percent from April.

"Are our policies a mistake, or are they correct? Is there really any other way," Abe asked rhetorically at a meeting of his Liberal Democratic Party (LDP) lawmakers. "Let us all win together," he said, raising his fist to applause. Abe's cabinet later officially set the vote for Dec. 14, NHK public TV said.

Abe has said he would delay for 18 months a second tax hike to 10 percent that had been slated for October 2015. He pledged that the second increase, which advocates say is needed to fund the bulging social security costs of a fast-ageing population, would go ahead in April 2017.

No general election needed to be held until late 2016, and surveys show around two-thirds of voters are wondering why Abe is taking the plunge now. "The whole reason is a bit unclear, or a bit trivial," said Yutaka Watanabe, a middle-aged tourist snapping a photo of the parliament building on Friday morning.

But the prime minister hopes to cement his grip on power before his support ratings slip too far. Next year, he plans to tackle unpopular policies such as restarting reactors that went off-line after the 2011 Fukushima nuclear crisis.

TRICKLE DOWN OR BOTTOM UP?

An Asahi newspaper poll published on Friday showed Abe's support fell to 39 percent - the lowest since he took office in December 2012 - and just a bit more than the 40 percent who do not back him.

Still, 37 percent said they would vote for the LDP in proportional representation districts, compared with 13 percent who planned to vote for the main opposition Democratic Party of Japan (DPJ). Thirty percent were undecided.

"Unfortunately, the DPJ has not recovered to a point where we can say to voters, 'Entrust the government to us'," DPJ Secretary General Yukio Edano told a news conference. The Democrats were trounced in 2012 after three years in power.

Edano said the DPJ wanted to give voters a choice between Abe's "trickle down" policies that critics say favor the rich and big firms, and the Democrats' "bottom up" strategy that focuses on the middle class.

Faced with a weak and divided opposition, the LDP and its junior partner, the Komeito party, are not expected to lose their majority in the lower house, where they held two-thirds of the 480 seats. There will be 475 seats up for grabs this time after reforms to rebalance between sparsely populated rural districts and dense urban areas.

Abe said he would resign if his coalition failed to win a majority, an outcome experts dismissed as almost impossible, though he could end up weakened if the LDP loses too many seats.