By Doina Chiacu and Nandita Bose

WASHINGTON (Reuters) - Kamala Harris will become the first U.S. vice president to visit Vietnam next month during a trip that will also include Singapore and is aimed at rallying an international coalition to curb China's growing influence.

Harris will discuss regional security, the global response to the COVID-19 pandemic, climate change, and "our joint efforts to promote a rules-based international order," according to spokesperson Symone Sanders.

Vietnam has emerged as the most vocal opponent of China's territorial claims in the South China Sea and has received U.S. military hardware, including coastguard cutters.

"President Biden and Vice President Harris have made it a top priority to rebuild our global partnerships and keep our nation secure, and this upcoming visit continues that work," the White House said in a statement.

Additional details were not immediately available.

U.S. Defense Secretary Lloyd Austin visited Vietnam on Thursday to nudge forward security ties with the country that have been slowly deepening as both countries watch China's activities in the South China Sea with growing alarm.

On Sunday, the United States shipped 3 million doses of the Moderna COVID-19 vaccine to former Cold War foe Vietnam.

Earlier this month, Deputy Secretary of State Wendy Sherman made a trip to the northern Chinese port city of Tianjin to meet Foreign Minister Wang Yi and other officials. The two sides appeared to stop short of actually negotiating anything, sticking instead to lists of established demands.

China's growing dominance has been a top concern for the Biden administration. During a recent trip to the Office of the Director of National Intelligence, President Joe Biden highlighted the threats posed by China.

He referred to President Xi Jinping as "deadly earnest about becoming the most powerful military force in the world, as well as the largest and most prominent economy in the world by the mid-40s, the 2040s."

This will not be Harris's first overseas trip. She recently visited Mexico and Guatemala with the aim of lowering migration from the region. During her trip she focused on issues such as economic development, food insecurity and women's issues

(Reporting by Nandita Bose and Doina Chiacu; Additional reporting by Aradhana Aravindan; Editing by Joe Bavier and Alistair Bell)