"We have no choice," said Masayuki Kichikawa, of Bank of America-Merrill Lynch. "This is kind of a very delicate matter for Mr. Abe."
That angers some groups who object to foreign influence over domestic policy, including those who view the plan as an American scheme to usurp Japan's sovereignty.
"Obama has threatened Japan and forced us into joining TPP," Takaaki Tabuchi, a financial consultant, shouted to a group of about 20 protesters who gathered near Tokyo's Shibuya train station late Thursday.
"Preserve our livelihoods. Reject TPP," they chanted, largely ignored by passers-by.
The protests this time, including a big gathering of farmers who conducted a rally at Tokyo's Hibiya Park on Tuesday, appear to lack the scale or passion of past anti-TPP demonstrations.
But Akira Banzai, head of Japan's Zenchu, the Central Union of Agricultural Cooperatives, vowed Friday to persist in resisting the trade deal.
"Along with farmers across the nation, I protest with outrage," Banzai said in a statement. "To protect our food, our livelihoods and our survival, we will staunchly resist TPP to the very end."
Abe said Japan must join the talks or miss its chance to have any say in negotiations on the trade pact, since the Obama administration has said it hopes to wrap up negotiations by the year's end, though including Japan could slow the process.
In Washington, Democratic lawmakers presented a letter addressed to Obama raising concerns that the pact may threaten the U.S. auto industry.
They contend that Japanese auto exports to the United States could increase if the United States eliminates its current 2.5 percent car tariffs and 25 percent truck tariffs.
Associated Press writer Mari Yamaguchi in Tokyo and Matthew Pennington in Washington contributed to this report.
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