WASHINGTON » While failing to seal a deal on his ambitious plan to expand trade in the Pacific Rim, President Barack Obama on Thursday said a long-stalled trade pact still can be finalized if Japan opens its markets and accepts more U.S. exports of everything from cars to farm goods.

"That’s my bottom line, and I can’t accept anything else," Obama said at a news conference in Tokyo.

After meeting privately with Japanese Prime Minister Shinzo Abe, the president said that "important progress" had been made in trying to wrap up the deal, adding: "I continue to believe we can get this done."

In Washington, opponents celebrated the lack of a final agreement of the proposed Trans-Pacific Partnership, known as the TPP, Obama’s effort to broker the largest trade pact in U.S. history.

After many setbacks, "TPP should be ready for burial," said Lori Wallach, director of Public Citizens Global Trade Watch, a group that opposes the deal.

U.S. business groups, which have lobbied for the trade agreement for four years, vowed to press on.

"The talks are alive and well, with more to be done, and they will be done," said Cal Cohen, president of the Emergency Committee for American Trade, a group of leading U.S. international business enterprises promoting the trade pact. He added the negotiations "are a marathon, not a sprint."

U.S. trade officials said more talks are expected in May.

Negotiators for the United States and Japan had scrambled to try to close a deal in advance of Obama’s four-nation visit to Asia, leading to high expectations on both sides.

In the end, the details again proved too intractable.

While exact minutia of the talks remain private, one of the biggest hurdles remaining is getting Japan and the United States to agree on tariffs for cars and crops.

In the United States, critics worry that Obama’s trade negotiators may lower or abandon automobile tariffs to win greater access to Japan’s markets for beef and pork, rice, dairy, sugar and wheat products. That would allow more Japanese cars to enter the U.S. at lower cost, angering the domestic auto industry.

At his news conference, Obama said it was time for the two nations to take "bold steps" to reach an agreement.

"There are always political sensitivities in any kind of trade discussions," Obama said. "Prime Minister Abe has got to deal with his politics. I’ve got to deal with mine."

But the president added: "All of us have to move out of our comfort zones and not just expect that we’re going to get access to somebody else’s market without providing access to our own."

The negotiations between the two economic superpowers have taken center stage since Japan last year became the 12th entrant to the pact, joining the United States, Australia, Brunei, Canada, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.

U.S. officials view the proposed deal as a potential goldmine for American businesses, with the 12 countries representing 40 percent of the global gross domestic product. And they say the opportunities will only grow, with Asia’s middle-class population, now at 500 million, set to explode in coming years.

Critics of the deal, both in Congress and among trade-watch groups, have long complained that negotiators should release more details of the talks to allow the public a glimpse of the big stakes. And many predict that even if Obama can finalize a deal with the 11 foreign countries, he’s unlikely to get it passed by Congress, with his trade agenda showing no signs of momentum on Capitol Hill in an election year. Opponents fear the deal will chase more American jobs overseas and only benefit corporations.

"It’s going to take more than a market-access deal with Japan for the TPP to become anything but dead-on-arrival in the U.S. Congress," said Arthur Stamoulis, executive director of the Citizens Trade Campaign, a coalition of labor, environmental, farm, consumer and human rights groups opposed to the pact.

With the negotiations now "so clearly at an impasse," Stamoulis said, "It’s time to take a step back, release what’s been proposed for public scrutiny and let people weigh in."

Wallach said that even if Japan and the United States reach an agreement, the talks could stumble with other countries over lingering disputes dealing with medicine patents, food-safety issues, financial regulations, Internet policies and environmental and labor standards, among others.

But with the administration promising more talks, Wallach said, the trade pact is "like some movie monster that will not die."

Cohen said U.S. negotiators will face difficult issues in finalizing a deal but predicted "a robust outcome."