GEOFF BENNETT: Today, President Biden hosted the leaders of Japan and the Philippines and sent a strong message of unity to Beijing.

Nick Schifrin has been following these developments and joins us now.

NICK SCHIFRIN: Geoff, the administration calls it the U.S.' greatest strength, a network of alliances and partnerships.

The U.S.' oldest ally in Asia is the Philippines.

And, today, the relationship is expanding in direct response to actions by China.

With a camera and water cannon, the Chinese Coast Guard takes direct aim at a Philippine supply ship.

For weeks, Beijing's boats have harassed and even bumped Philippine boats trying to resupply a Philippine ship purposely grounded two decades ago inside the Philippines' Exclusive Economic Zone.

The U.S. calls these actions unlawful and coercive and is recommitted to defending its treaty ally, including today at the White House.

JOE BIDEN, President of the United States: Any attack on Philippine aircraft, vessels or armed forces in the South China Sea would invoke our mutual defense treaty.

NICK SCHIFRIN: This was the first ever trilateral summit between the leaders of the U.S., Philippines and Japan.

Philippines President Ferdinand Marcos Jr.: FERDINAND MARCOS JR., President of the Philippines: Today's summit is an opportunity to define the future that we want and how we intend to achieve it together.

NICK SCHIFRIN: Japanese Prime Minister Fumio Kishida: FUMIO KISHIDA, Japanese Prime Minister (through translator): Japan, the U.S. and the Philippines are maritime nations connected by the Pacific Ocean and our natural partners.

NICK SCHIFRIN: This week, the three countries, along with Australia, conducted their first ever joint naval drills.

And, yesterday, the U.S. and Japan announced their most significant military cooperation upgrade in decades.

It's an effort to deter China by creating an arc of military alliances willing to confront Beijing together.

The U.S. had already agreed with Japan and the Philippines to expand U.S. presence on islands that are closer to Taiwan than they are to the capitals Manila and Tokyo.

FUMIO KISHIDA: China's current external stance and military actions present unprecedented and the greatest strategic challenge.

RODRIGO DUTERTE, Former President of the Philippines: We are deeply concerned about the ongoing trade war.

NICK SCHIFRIN: The Philippines' agreements continue to reverse the deterioration of bilateral relations under former President Rodrigo Duterte, and they embrace a legacy of cooperation under Ferdinand Marcos Sr., whose 66-year-old son today is trying to fortify his nation against Beijing.

FERDINAND MARCOS JR.: Facing the complex challenges of our time requires concerted efforts on everyone's part, a dedication to a common purpose, and an unwavering commitment to the rules-based international order.

NICK SCHIFRIN: Today's announcements also included the first Philippines infrastructure investment from a new U.S.-backed initiative designed to counter China's Belt and Road investments.

To discuss this more, I'm joined by Zack Cooper, a senior fellow at the Washington-based think tank the American Enterprise Institute.

Zack Cooper, thanks so much.

Welcome back to the "NewsHour."

How significant are the announcements that we heard not only today from the U.S. and the Philippines, but yesterday from the U.S. and Japan?

ZACK COOPER, Senior Fellow, American Enterprise Institute: These are huge announcements.

In both countries, the United States is making real progress.

I think the U.S. and Japan are announcing 70 initiatives.

But, in my mind, the most important are efforts to make sure that the U.S. and Japan can cooperate together on both capability development -- so, this is building new systems together, maintaining them together -- but also advancing our command-and-control facilities, ensuring that we can fight together more effectively if we end up in a contingency, especially one with China.

And then, in the Philippines, you have got a raft of announcements mostly focused on development in the Philippines, which is critical for people there, and also on cooperating more closely with Manila in the South China Sea.

So, I think, in both countries, these are going to be well-received and are real important progress.

They signify important progress at a critical moment, when China is pressing hard in the region.

NICK SCHIFRIN: And when it comes to what the U.S. gains from this militarily, what does this allow the U.S. military to have in the region that it didn't have a few years ago?

ZACK COOPER: At the moment, in the next couple of months, probably nothing.

But, over the long term, these are the foundational agreements that will allow the United States to be much more effective in how it operates in both the Philippines and in Japan.

In the Philippines, we have learned the U.S. has to have a sustainable presence, which means we have to have support from the people in the Philippines.

We had -- we didn't have that for part of our history, especially if you look back at the 1990s.

And these economic deals are going to have to show that the United States and others can bring real development to the Philippines alongside American forces that will help to protect Philippine interests.

In Japan, we're seeing the United States really build out its infrastructure, not just the people and the places that we're operating from, but also the command infrastructure to make sure that, if we're in a crisis, we can work closely with our Japanese allies.

So, this probably won't result in major changes today, tomorrow, but next year and the years to come, these are going to be really important moves.

NICK SCHIFRIN: I mentioned at the top of the story, and you just mentioned it now, those Chinese actions that the Coast Guards have taken off the Second Thomas Shoal in the South China Sea.

U.S. officials, as you know, are worried this could become a crisis.

Do you believe this could become a real U.S.-China crisis?

ZACK COOPER: I do.

I have been worried about Second Thomas Shoal for a long time.

If you look back at the recent crises we have had, Second Thomas Shoal has been among the most problematic, in part because China and the Philippines have very different views about what the status quo is and what should happen there.

And it's incredibly important to the United States because the U.S. has a mutual defense treaty with the Philippines, which specifies that an armed attack on a Filipino public vessel would call into question the U.S. treaty alliance guarantee.

And we have gotten very close to this in recent months, with China using water cannons against Philippine ships, with rammings happening almost on a weekly basis.

And so these are very, very serious incidents.

And I think you're seeing the Biden team step up and say, we just can't accept this level of risk forever.

And that's why they're moving now to tie Biden and Marcos more closely together and trying to do it with other countries like Japan and Australia.

NICK SCHIFRIN: I mentioned before the economic investments as part of today's announcement of the Philippines.

You have mentioned them as well.

Given the military progress that we have been discussing, has the U.S. made as much economic progress in the region?

ZACK COOPER: The short answer is no.

We have polling data out recently on this that shows that most countries in the region have actually been more convinced over the last year that the U.S. is losing the level of economic engagement they wanted to see.

The economic efforts by the Biden team, especially something called the Indo-Pacific Economic Framework, have fallen flat in much of Southeast Asia.

And so this is probably the missing leg of the U.S. strategy in the region.

The U.S. is doing better in the Philippines than in the rest of Southeast Asia.

But there's a huge amount of work to do for the Biden team to convince Southeast Asian leaders and experts and publics that the U.S. is going to be there for the long haul and that the U.S. is going to continue to invest in the region, the way it has for so long.

NICK SCHIFRIN: Biden administration officials tell me they're trying to institutionalize days like today set on the calendar into the future, things like summits, whether bilateral or trilateral.

How much do we know if Donald Trump would maintain these kinds of minilateral arrangements, as we call them, if he were to become president again?

ZACK COOPER: I think it really depends on the institution that we're talking about.

A group like the Quad, which involves India, Japan, Australia, and the United States, that seems to me to be one that Trump is likely to continue supporting, so too with AUKUS, the Australia, United States, United Kingdom agreement.

I think some of these other trilaterals, especially if they involve countries that Trump isn't particularly supportive of, which -- and, here, I would look towards Europe -- those could be harder.

But I think, in Asia, the logic of these minilateral arrangements is quite clear.

And so I would hope that the Trump administration would do as they did in the first term and maintain these if Trump is elected in November.

NICK SCHIFRIN: Zack Cooper of the American Enterprise Institute, thanks very much.

ZACK COOPER: Thanks, Nick.