Top government officials have signaled that Prime Minister Yoshihiko Noda plans to make a decision before he leaves for the annual Asia-Pacific Economic Cooperation summit in Hawaii, where President Barack Obama and 20 other regional leaders will gather this weekend.

Several Cabinet ministers and business leaders have spoken out strongly in favor of joining the Trans-Pacific Partnership, a free trade bloc made up of four small economies — Chile, New Zealand, Brunei and Singapore. The U.S., Australia, Vietnam, Malaysia and Peru are already in talks to join.

Some APEC member economies see the Pacific trade pact as a building block for a free trade area that encompasses all of Asia and the Pacific, covering half the world’s commerce and two-fifths of its trade.

Media reports say Noda plans to explain to the public why Japan, the world’s third-biggest economy, should join the Pacific pact at a press conference Thursday. The ruling party is split over the issue, with a vocal ex-agricultural minister and others actively campaigning against it. Introducing more competition just as Japan is trying to recover from the March tsunami disaster and nuclear power plant crisis is bad timing, critics say.

Joining the so-called TPP would mean eliminating tariffs on imports into all member economies — a move that Japan’s major manufacturers say will improve access to foreign markets, enhance regional trade and investment and keep Japan from falling behind regional trading rivals.

Only 16 percent of Japan’s trade is covered by free trade agreements, compared with 71 percent for Singapore and 36 percent for South Korea — if the Korean legislature approves a free-trade deal with the U.S. that was ratified by Congress last month.

Proponents say expanding free trade will breathe new life into Japan’s sagging economy, burdened by a surging yen and shrinking population, and allow companies to better tap into Asia’s rapid growth. Yet if Japan joins negotiations it could still be several years before any agreement to reduce tariffs comes into effect.

"It is crucial for Japan to capitalize on Asia’s economic growth," said Takeshi Niinami, CEO of Lawson Inc., a Japanese convenience store chain.

Joining negotiations now would also allow Japan to help shape the deal, argues Trade Minister Yukio Edano.

"Time is running out," Edano said at a recent debate. "We are already losing out quite a bit in the rule-making process. There is no doubt about that. We must decide whether to join while there still is a room for us to have a say or just accept what’s already made."

Farmers — who have an outsized influence in parliament despite accounting for just 1.5 percent of the economy — say they will be destroyed if protective tariffs on rice and other agricultural goods are cut. They say they can’t compete with huge farms in the U.S. and Australia.

"I’m probably going to go bankrupt" if Japan joins the free trade zone, said Masashi Yonebayashi, a 61-year-old rice and wheat farmer in Shinshinotsu, on the northern island of Hokkaido. "Newspapers around here are saying incomes will fall by 60 and 70 percent, but in actuality it’ll be hard to sell anything."

At a rally Saturday in downtown Tokyo, former Agricultural Minister Masahiko Yamada said the trade pact is not a threat only to Japan’s farmers, but it could also take away jobs and weaken food safety and quality standards.

"We must block Japan’s participation," he told a big cheering crowd as he stood on the roof of a campaign vehicle. "TPP is not a problem just for the farming. It affects every corner of our daily life."

Free trade can be an emotional issue elsewhere in the region, too. In Seoul last week, protesters claiming much the same thing scuffled with riot police over the trade deal with the U.S.

Imported rice is taxed at 778 percent in Japan, wheat at 252 percent, butter at 360 percent — tariffs that critics say have contributed to making Japan’s farming sector inefficient and uncompetitive. Also, the government has subsidized Japan’s thousands of rice farmers, many of whom own tiny lots while working other jobs.

Edano, the trade minister, argues that Japanese farming needs overhauling anyway, and that joining the trade agreement would help revitalize Japan’s dying rural areas by bringing in new businesses.

But critics argue that it is very bad timing to allow competition to intensify as Japan is trying to recover from the tsunami. Farming has been hurt amid concerns about radiation in fresh produce, particularly in Fukushima — the prefecture that is home to the nuclear power plant damaged by the tsunami.

Critics also say the government is moving too hastily on such a big decision, and that little has been done to consult with or prepare farmers. Former Prime Minister Naoto Kan first introduced the possibility about a year ago. A decision was initially expected in June, but that was put off because of the tsunami and nuclear disasters.

"Now is not the time to discuss international competition," said Masaru Kaneko, an economy professor at Keio University.

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Associated Press Writer Mari Yamaguchi contributed to this report.