U.S. Vice President Kamala Harris said during her trip to Vietnam on Wednesday that the United States will provide an additional 1 million coronavirus vaccine doses to the country to help it fight the pandemic.

During her talks with Vietnamese officials, including President Nguyen Xuan Phuc, in the capital Hanoi, Harris also served notice to China over its claims in the South China Sea, where Vietnam has territorial disputes with its northern neighbor.

The United States has already donated roughly 5 million doses of vaccine to Vietnam, with Harris earlier saying the United States intends to serve as "an arsenal of safe and effective vaccines for our entire world."

The vice president said the Defense Department has committed to provide 77 ultra-low temperature vaccine freezers to assist vaccination distribution efforts in all 63 of Vietnam's provinces.

Later Wednesday, she attended the opening ceremony of the Southeast Asia regional office of the U.S. Centers for Disease Control and Prevention.

Vietnam has been grappling with surging virus cases since April but its vaccination rate remains low. As of Sunday, less than 2 percent of the population had been fully vaccinated.

The CDC's newly created regional office in Hanoi covers Vietnam and other member countries of the Association of Southeast Asian Nations as well as Papua New Guinea, and is expected to serve as a base for coordination with those countries and making a rapid response to infectious diseases.

Harris also criticized China over its sweeping claims in the South China Sea and emphasized the need to keep its behavior in check, indicating that Washington hopes U.S. vessels, including aircraft carriers, will continue to make port calls in Vietnam.

"We need to find ways to pressure and raise the pressure, frankly, on Beijing to abide by the United Nations Convention on the Law of the Sea, and to challenge its bullying and excessive maritime claims," Harris said during a portion of her talks with the Vietnamese president that was open to the media.

The vice president also noted that the administration of President Joe Biden supports sending another used U.S. Coast Guard cutter to Vietnam, contingent on the congressional approval.

According to a White House fact sheet, "This cutter would complement two other U.S.-provided cutters, a fleet of 24 patrol boats, base facilities, piers, law enforcement training, and other joint activities that bolster Vietnam's capacity to contribute to maritime security in the South China Sea."

At the outset of her separate talks with Prime Minister Pham Minh Chinh, Harris said, "We are grateful for Vietnam's constructive leadership in upholding freedom of the seas."

And we will continue to work with you to push back against threats to the rule-based international order," she added, in an evident swipe at China.

Harris arrived in Vietnam, the final leg of her two-nation tour in Southeast Asia, on Tuesday as the first sitting U.S. vice president ever to visit the country.

In a speech in Singapore earlier that day, she denounced China's assertion of its territorial claims in the South China Sea as unlawful.

"Beijing's actions continue to undermine the rules-based order and threaten the sovereignty of nations. The United States stands with our allies and partners in the face of these threats," she said, pledging that Washington will pursue a free and open Indo-Pacific.

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