UPDATE1: Japan PM Kan announces his resignation+

TOKYO, Aug. 26 Kyodo -
(EDS: UPDATING WITH NEW DETAILS)
Prime Minister Naoto Kan announced his resignation Friday after facing persistent criticism from both ruling and opposition lawmakers, spinning Japan's revolving-door leadership yet again toward picking his successor next week.
''Today, I'd like to resign as head of the Democratic Party of Japan...and then once the new leader is picked, I will quickly quit as prime minister,'' Kan told a meeting of the ruling party, after almost 15 months in office. ''While there was some harsh criticism, despite that, I am really thankful for the support you have given me.''
The DPJ's presidential election to choose a successor to Kan will take place Monday, when only its 398 lawmakers will be eligible to vote.
Kan expressed no regrets about leaving office, nearly three months after first indicating he would do so, telling a news conference later, ''In a tough environment, I feel that I did what I had to do'' and have ''a certain sense of accomplishment.''
The 64-year-old premier also suggested that he has no immediate plans to quit as a lawmaker, renewing his pledge to work toward reconstructing areas devastated by the March 11 earthquake and tsunami, and turning Japan into a country that does not need to rely on nuclear energy.
Five candidates, including former Foreign Minister Seiji Maehara, 49, and current Economy, Trade and Industry Minister Banri Kaieda, 62, will likely run in the election, an unusually large number since the party was formed in 1998.
Finance Minister Yoshihiko Noda, 54, Agriculture, Forestry and Fisheries Minister Michihiko Kano, 69, and former Land, Infrastructure, Transport and Tourism Minister Sumio Mabuchi, 51, have also made up their minds to aim for the top post.
Maehara has been the most popular of the candidates among voters surveyed in recent media polls. If his bid is successful, he would be the youngest prime minister in Japan's postwar history.
But it remains uncertain whether Maehara will be able to make his dream come true as he has failed to win support from Ichiro Ozawa, a power broker in the ruling party who heads the biggest faction and effectively controls about one-third of the votes to elect the new leader.
Ozawa and Kan's predecessor, Yukio Hatoyama, have decided to back Kaieda, according to lawmakers who spoke on condition of anonymity.
Political horse-trading is intensifying between the candidates. Former Environment Minister Sakihito Ozawa and Shinji Tarutoko, former chairman of the DPJ's Diet Affairs Committee, on Friday gave up on their plans to run in the race and decided to integrate their support bases with other candidates.
The lawmakers said the former environment minister and his allies will also support Kaieda, who had tense relations with Kan due to the prime minister's opposition to nuclear power.
Since taking office in June last year, Kan has struggled with low support ratings, a relentless power struggle within the DPJ and a divided Diet, with combative opposition parties controlling the upper house and hampering the passage of legislation.
Kan, already Japan's fifth leader since 2006, said in early June that he would hand over his post to the DPJ's next generation after a certain level of progress had been made in reconstructing the disaster-stricken northeastern region and containing the nuclear crisis at the Fukushima Daiichi power plant.
He later explained that the handover would take place if three conditions were fulfilled.
They were the parliamentary passage of three bills -- the second extra budget, a bill to allow the government to issue deficit-covering bonds to secure about 40 percent of the revenue needed for this fiscal year's initial budget and a bill to promote the use of renewable energy.
On Friday, the last two bills cleared the Diet with sufficient support in the opposition-controlled House of Councillors.
Shortly after Kan took the helm, his government enjoyed approval ratings of around 60 to 70 percent, marking a dramatic recovery from those in the final days of the Cabinet of Hatoyama, who was the first leader after the DPJ's rise to power in September 2009.
But high expectations of Kan -- Japan's first leader in many years not born into a blue-blood political family -- waned and approval ratings for the Cabinet have fallen below 20 percent in recent days.
The slump was first triggered by Kan's remarks suggesting a possible hike in the consumption tax, which led to the DPJ's stinging defeat in the House of Councillors election just a month after his inauguration and resulted in the divided Diet.
Later, among other things, Kan came under fire not only from the opposition but also ruling party lawmakers for his perceived lack of leadership in dealing with the March disaster that claimed the lives of more than 15,000 people and triggered the world's worst nuclear crisis in 25 years.