U.S. President Joe Biden's trip to Asia sought to put on full display the robust bilateral alliances with Japan and South Korea, as well as the evolving Quad partnership with Japan, Australia and India in the face of the looming security threats and economic challenges posed by China.

But the development of a deeper and broader alignment across the Indo-Pacific that can push back against China's assertiveness seems to remain elusive, as indicated by the mixed response to Russia's invasion of Ukraine and the vagueness of a just-launched U.S. economic engagement initiative in the region.

During his three-day visit to Japan through Tuesday, Biden suggested that a firm global response to Russian President Vladimir Putin's "barbarism" in Ukraine may shape the future behavior of China, which seeks to bring Taiwan into its fold, by force if necessary.

The "expectation" is that China will not try to seize the self-ruled island by force, but it "depends upon just how strongly the world makes clear that that kind of action is going to result in long-term disapprobation by the rest of the community," Biden said at a press conference Monday alongside Japanese Prime Minister Fumio Kishida.

U.S. President Joe Biden speaks during a summit of the "Quad" group of Indo-Pacific democracies -- the United States, Japan, Australia and India -- in Tokyo on May 24, 2022. (Kyodo) ==Kyodo

But experts have been doubtful that U.S. coalition-building efforts will result in any reassurance that many countries across the Indo-Pacific would stand up in the event of a potential military attack on Taiwan by China.

"We shouldn't assume that just because a lot of countries, especially some of the large economies, took action on Russia that they would necessarily do that in the China context," said Zack Cooper, an expert on U.S.-China competition and Asia security issues at the American Enterprise Institute.

"My sense is the coalition on China would be harder to build and probably smaller," he added, apparently in mind of the possible repercussions of acting against China, whose economy is far larger than Russia's and more deeply integrated with the rest of the world.

"We also have to remember that even though the sanctions (imposed on Russia from the West) have been pretty tough, they didn't actually stop Putin from invading in the first place."

In the Ukraine crisis, the Biden administration has hailed the "unprecedented commitments" from Indo-Pacific nations to support Ukraine and impose costs on Russia for its aggression, citing Japan, Australia, Singapore, South Korea and New Zealand.

But the countries are all close U.S. allies and partners, and a gaping hole in the united front has been India -- the only Quad member shying away from condemning Russia and from taking punitive steps due to its heavy reliance on Moscow as a weapons supplier.

Apparently in consideration of India's stance, a joint statement of the Quad leaders released after their meeting Tuesday in Tokyo did not mention Russia by name.

India's failure to stand firm with the other democracies over the Ukraine crisis has stirred disappointment among U.S. lawmakers, raising a question as to whether the South Asian country, which holds key potential to act as a counterbalance to China, can be viewed as a reliable partner.

Cooper said India's neutral position on the Ukraine situation is not likely to undermine the role of the Quad, as the group's focus is on China rather than Russia.

White House Indo-Pacific coordinator Kurt Campbell described India as a "swing state," a term in American politics referring to a state where Republican and Democratic candidates have similar levels of support, making its voting patterns unpredictable from one election cycle to the next.

"It is in all of our best interests to try to work with India over time to bend its trajectory more to the West," he said in early May at an event at the Center for Strategic and International Studies.

Although the Quad is "important," there is a need to realize its "limitations," said Joseph Nye, a former U.S. assistant secretary of defense for international security affairs, during a recent webinar organized by the New York-based Japan Society.

India is the only Quad member sharing a land border with China and it sees its friendly ties with Russia as leverage in dealing with a border conflict with Beijing, which resulted in a deadly clash in 2020.

The Quad, formed to coordinate the response of the four countries to the 2004 Indian Ocean earthquake and tsunami, had a dormant period amid leadership changes and concerns about economic repercussions from China. But the group was revived in 2017 and gained traction amid the members' deepening concerns over China's behavior.

The fact that New Delhi is willing to "meet formally with Japan and Australia and the U.S. is a huge step forward," given that India was originally "very scared to do much with the Quad" out of concerns of antagonizing China, the Harvard University professor emeritus said.

"But we shouldn't think of trying to push it into a formal defense alliance. The Indians aren't ready for that yet," he added.

While differences among the Quad members over Russia are likely to persist, the Biden administration is also facing headwinds over what is deemed its primary tool for economic engagement in the Indo-Pacific region.

Biden formally announced the launch of the Indo-Pacific Economic Framework for Prosperity, or IPEF, on Monday, joined by a dozen countries including Japan, India, Singapore, South Korea and Vietnam.

Although the initiative has been touted as a "21st-century economic arrangement" to tackle new challenges such as setting standards for the digital economy and ensuring secure supply chains, the United States has said the IPEF will not be a traditional free trade agreement involving tariff-cutting commitments.

Trade experts are skeptical as to whether the scheme can provide incentives for participation without offering greater market access to the world's largest economy.

(From L) Japanese Prime Minister Fumio Kishida, U.S. President Joe Biden and Indian Prime Minister Narendra Modi attend a photo session at the start of the launch event of the Indo-Pacific economic framework, or IPEF, in Tokyo on May 23, 2022. (Kyodo) ==Kyodo

Riley Walters, an expert on East Asia at the Hudson Institute, said the "economic gains from the framework are questionable" and the IPEF "looks disappointingly unambitious and is unlikely to usher in a new era of U.S. economic engagement in the region."

Meanwhile, the prospects of ties between the two closest U.S. allies in Asia -- Japan and South Korea -- seem to have brightened in the wake of the recent launch of conservative leadership in South Korea as it pursues a more pro-U.S. policy and larger role in regional affairs.

Ryo Sahashi, an associate professor specializing in international politics in East Asia at the University of Tokyo, said he is optimistic about increased cooperation between the two countries, as well as with the United States, such as over semiconductor supply chain issues.

But he also acknowledged that disputes over wartime history which have longed marred the bilateral ties will not be easily overcome, suggesting the risk of potential flare-ups.

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