"I got a call from the head of Vietnam, desperately wants to meet with me when I go to the G20. He wants to elevate us to a major partner, along with Russia and China," Biden told dozens of donors to his 2024 re-election campaign at an event in Freeport, Maine.

At a meeting in April, Vietnamese Prime Minister Pham Minh Chinh and U.S. Secretary of State Antony Blinken expressed a desire to deepen their ties as Washington seeks to solidify relations with partners in Asia to counter an increasingly assertive China.

Blinken had expressed hope then that this could happen "in the weeks and months ahead."

Vietnam's embassy in Washington did not immediately respond to a request for comment on Biden's remarks.

Washington has been working to elevate ties with Hanoi to a "strategic" partnership from one that for the past decade has been called "comprehensive," although Vietnam has been cautious given the risk of antagonizing China, a giant neighbor that supplies key inputs for its vital export trade, or Russia, another traditional partner.

Officials have not said what this closer relationship might entail, but experts say it could include increased military cooperation and U.S. weapons supplies.

Washington and U.S. defense firms have openly said they want to bolster military supplies to Vietnam - so far largely limited to coastguard ships and training aircraft - as the country seeks to diversify away from Russia, which remains its main supplier.

Military deals with the U.S. face potential hurdles, however, including the possibility of their being held up by U.S. lawmakers critical of Vietnam's human rights record.