Addressing a summit of the 10-member Association of Southeast Asian Nations, Vice President Kamala Harris said the region was a U.S. priority. The opening session of their meeting at the State Department on Friday would focus on maritime security and health issues, she said.
"The United States and ASEAN have shared a vision for this region, and together we will guard against threats to international rules and norms," she said.
"We stand with our allies and partners in defending the maritime rules-based order, which includes freedom of navigation and international law," she said.
"As an Indo-Pacific nation, the United States will be present and continue to be engaged in Southeast Asia for generations to come," Harris added.
Harris said the United States would continue to respond with ASEAN to the threat of Covid-19, having already donated more than 115 million vaccines to the region.
"As long as Covid is present in any one country, it affects us all," she said.
President Joe Biden started the summit, bringing together Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam, by hosting a dinner for the leaders at the White House on Thursday.
Myanmar's leader was excluded over a coup last year and the U.S. treaty ally the Philippines is in transition after an election, though Biden spoke to the country's president-elect, Ferdinand Marcos Jr., on Wednesday. The country was represented by its foreign affairs secretary.
The Biden administration hopes the efforts will show the countries that Washington remains focused on the Indo-Pacific and the long-term challenge of China, which it views as its main competitor despite the crisis in Ukraine.
On Thursday Washington promised $150 million to help improve infrastructure, security, pandemic preparedness and on other projects in ASEAN, but U.S. spending pales in comparison to that of China.
In November alone, Beijing pledged $1.5 billion in development assistance to them over three years to fight Covid and fuel economic recovery. U.S. officials concede Washington needs to step up its game in the region.
New U.S. commitments will include deployment of a U.S. Coast Guard vessel to the region to help counter what Washington and regional countries have described as China's illegal fishing.
Biden is working on more initiatives, including "Build Back Better World" infrastructure investment and an Indo-Pacific Economic Framework (IPEF). But neither are finalized.
The summit marks the first time that ASEAN's leaders gathered as a group at the White House and in Washington and their first meeting hosted by a U.S. president since 2016.
Concern over China
ASEAN countries share many of Washington's concerns about Chinese assertiveness, including Beijing's claim of sovereignty over vast swathes of the South China Sea where Vietnam, the Philippines, Brunei and Malaysia have rival claims.
But they also remain cautious about siding more firmly with Washington, given their predominant economic ties with Beijing and limited U.S. economic incentives.
They have also been frustrated by a U.S. delay in detailing plans for economic engagement since former President Donald Trump quit a regional trade pact in 2017.
Malaysian Prime Minister Ismail Sabri Yaakob said on Thursday Washington should adopt a more "active" trade and investment agenda with ASEAN.
The IPEF is set to be launched on Biden's trip to Japan and South Korea next week. But it does not currently offer the expanded market access Asian countries crave, given Biden's concern for American jobs.