President Biden showed off a slice of his Delaware hometown of Wilmington to the leaders of Australia, Japan and India as he hosted what is likely the last gathering of the Indo-Pacific partnership that has grown in prominence under his White House tenure.

When Mr. Biden began his presidency he looked to elevate the so-called Quad, which until then had only met at the foreign minister level, to a leader-level partnership as he tried to pivot U.S. foreign policy away from conflicts in the Middle East and toward threats and opportunities in the Indo-Pacific. This weekend's summit is the fourth in-person and sixth overall gathering of the leaders since 2021.

"It will survive way beyond November," Mr. Biden declared as the leaders gathered at the Archmere Academy, his high school alma mater in nearby Claymont for joint talks.

Following their meeting, the four leaders released a joint statement they titled the "Wilmington Declaration," which seeks to "reaffirm our steadfast commitment to a free and open Indo-Pacific that is inclusive and resilient."

The extensive resolution, described as a "vision statement," touched on a variety of issues including regional conflicts, including the Israel-Hamas war and the Russian invasion of Ukraine, maritime security, technology, clean energy, cyber security and health.

Biden hosts leaders at his Wilmington home and high school alma mater

The president, who has admitted to an uneven track record as a scholar, also seemed tickled to get to host a gathering with three world leaders at the school he attended more than 60 years ago. He welcomed each of the leaders individually for one-on-one talks at his nearby home before they gathered at the school for talks and a formal dinner.

"I don't think the headmaster of this school thought I'd be presiding over a meeting like this," Mr. Biden joked to fellow leaders.

Australian Prime Minister Anthony Albanese, Indian Prime Minister Narendra Modi and Japanese Prime Minister Fumio Kishida came for the summit before their appearances at the U.N. General Assembly in New York next week.

"This place could not be better suited for my final visit as prime minister," said Kishida, who like Mr. Biden, is set to soon leave office.

Earlier, the president warmly greeted Kishida when he arrived at the residence on Saturday morning and gave the prime minister a tour of the property before they settled into talks. Kishida, according to the prime minister's office, thanked Biden at the outset of their meeting for inviting him to meet at his home.

White House officials said holding the talks at the president's house, which sits near a pond in a wooded area several miles west of downtown, was intended to give the meetings a more relaxed feel.

White House national security adviser Jake Sullivan described the vibe of Mr. Biden's one-on-one meeting with Albanese, who stopped by the house on Friday, as "two guys — one at the other guy's home — talking in broad strokes about where they see the state of the world." He said Mr. Biden and Albanese also swapped stories about their political careers.

The Australian leader remarked that the visit had given him "insight into what in my view makes you such an extraordinary world leader."

Modi also stopped by the house on Saturday to meet with Mr. Biden before the leaders gathered for their joint talks at Archmere.

"There cannot be a better place than President Biden's hometown of Wilmington to celebrate the 20th anniversary of the Quad," Modi said.

Reporters and photographers were prohibited from covering Mr. Biden's individual meetings with the leaders, and Biden does not plan to do a news conference — a question-and-answer appearance that is typical at such international summits.

What Biden hopes to accomplish with the summit

As part of the summit, the leaders announced new initiatives to bolster maritime security in the region — with enhanced coast guard collaboration through the Pacific and Indian oceans — and improved cooperation on humanitarian response missions. The measures are meant to serve as a counterweight to an increasingly assertive China.

"We are seriously concerned about the situation in the East and South China Seas," the Wilmington Declaration read. "We continue to express our serious concern about the militarization of disputed features, and coercive and intimidating maneuvers in the South China Sea."

Mr. Biden and Modi had been expected to discuss Modi's recent visits to Russia and Ukraine as well as economic and security concerns about China. Modi is the most prominent leader from a nation that maintains a neutral position on Russia's invasion of Ukraine.

The Wilmington Declaration noted that all four leaders have visited Ukraine since the war there began and reiterated "the need for a comprehensive, just, and lasting peace in line with international law, consistent with the purposes and principles of the UN Charter, including respect for sovereignty and territorial integrity."

Sullivan said "that countries like India should step up and support the principles of sovereignty and territorial integrity" and that "every country, everywhere, should refrain from supplying inputs to Russia's war machine."

The gathering was also an opportunity for Mr. Biden and Japan's Kishida to bid each other farewell.

Mr. Biden and Kishida, who are both stepping away from office amid sliding public support, count the tightening of security and economic ties among the U.S., Japan and South Korea as one of their most significant accomplishments. The two leaders sat down for their wide-ranging, one-on-one conversation on Saturday morning.

The improved relations between Japan and South Korea, two nations with a deep and complicated history that have struggled to stay on speaking terms, have come amid worrying developments in the Pacific, including strides made by North Korea in its nuclear program and increasing Chinese assertiveness.

The Wilmington Declaration condemned "North Korea's destabilizing ballistic missile launches and its continued pursuit of nuclear weapons in violation of multiple UN Security Council resolutions," adding that its "launches pose a grave threat to international peace and stability."

Mr. Biden commended Kishida for demonstrating "courage and conviction in strengthening ties" with South Korea, according to the White House. They also discussed China's "coercive and destabilizing activities" in the Pacific, Russia's war against Ukraine and emerging technology issues.

On the Israel-Hamas war, the Wilmington Declaration affirmed "the imperative of securing the release of all hostages held by Hamas" in a deal that "would bring an immediate and prolonged ceasefire in Gaza."

The declaration also called for "significantly increase deliveries of life-saving humanitarian assistance throughout Gaza as well as the crucial need to prevent regional escalation."

Tension surrounds Nippon Steel's proposed acquisition of U.S. Steel

The U.S. and Japan are negotiating through a rare moment of tension in the relationship. Mr. Biden, as well as Vice President Kamala Harris and former President Donald Trump, the two candidates in the 2024 presidential election, have opposed a $15 billion bid by Japan's Nippon Steel to take over American-owned U.S. Steel.

Biden administration officials indicated this week that a U.S. government committee's formal assessment of the proposed deal has yet to be submitted to the White House and may not come until after the Nov. 5 election.

Sullivan pushed back against speculation that the expected timing of the report could suggest Mr. Biden is having second thoughts about his opposition to the deal.

The Biden administration promised that the leaders would issue a joint statement containing the strongest-ever language on China and North Korea to be agreed upon by the four countries.

The leaders Saturday also rolled out a new collaboration aimed at reducing cervical cancer in the Indo-Pacific. The new partnership is related to Biden's Cancer Moonshot Initiative, a long-running passion project of the president and his wife, first lady Jill Biden, aimed at reducing cancer deaths. The Bidens' son Beau died in 2015 at age 46 of brain cancer.

As Mr. Biden's time in office draws down, the White House also was celebrating the bipartisan, bicameral formation of a "Quad Caucus" in Congress meant to ensure the longevity of the partnership regardless of the outcome of the November election.