HANOI—U.S. Secretary of State Mike Pompeo is wrapping up an anti-China tour of Asia in Vietnam as the fierce American presidential election race enters its final stretch.

With just four days left in the campaign in which China has been a central theme, Pompeo was visiting Hanoi on Friday ostensibly to celebrate 25 years of U.S.-Vietnam relations. But as he has at his previous stops in India, Sri Lanka, the Maldives and Indonesia, Pompeo is expected to highlight the Trump administration’s antipathy toward China, its handling of the coronavirus pandemic, its human rights record and aggressiveness towards its smaller neighbors.

Those issues, particularly the Chinese origin of the virus, have been highlighted by President Donald Trump as he seeks to beat back a stiff reelection challenge from former Vice President Joe Biden in the Nov. 3 polls. Trump has sought to paint Biden as weak on China and beholden to it, repeatedly raising questions about alleged connections between Biden’s son, Hunter, and Chinese businesses.

Vietnam was a late addition to Pompeo’s itinerary and has numerous concerns about Chinese policies in the region. Those range from Beijing’s territorial and maritime claims in the South China Sea to its development activities along the Mekong River, which runs through much of mainland Southeast Asia and is a regional lifeline.

In a statement released ahead of Pompeo’s arrival in Vietnam, the State Department attacked China for reneging on cooperation pledges with other Mekong countries and for aggressively pursuing suspect claims in the South China Sea.

China’s “malign and destabilizing actions in the Mekong region, including manipulation of Mekong river water flows, negatively affect millions of people who depend on the river for their livelihoods,” it said.

“The United States stands with our Indo-Pacific allies and partners in protecting their sovereign rights to offshore resources in the South China Sea, consistent with their rights and obligations under international law,” it said. It noted that earlier this year, Pompeo had rejected outright nearly all of Beijing’s maritime claims in the South China Sea.

“The United States rejects (China’s) maritime claims to the waters surrounding Vanguard Bank off Vietnam’s coast,” the statement said, “We will oppose any efforts aimed at undermining the rules-based maritime order in the South China Sea or elsewhere.”

China has pressed ahead with attempts to enforce its claims to much of the South China Sea and has ignored an arbitration ruling won by the Philippines that invalidated China’s claims.

Pompeo arrived in Vietnam from Indonesia, where he praised Indonesian leadership in the Association of Southeast Asian Nations for pushing back on what he called China’s “unlawful” South China Sea claims and denounced Beijing for its treatment of religious minorities, calling it “the gravest threat to the future of religious freedom.”

Pompeo had traveled to Indonesia from the Maldives, Sri Lanka and India on stops where he steadily ratcheted up the pressure on China, which has rejected U.S. concerns and accused him and others in the Trump administration of fanning the flames of a new Cold War.

In the Maldives, Pompeo announced the United States would for the first time open an embassy in the Indian Ocean archipelago, a move that reflects growing U.S. concern about increasing Chinese influence and what he called “its lawless and threatening behavior” in the Indo-Pacific region.

Just hours earlier in Sri Lanka, Pompeo had accusing China of being a “predator” in smaller countries by exploiting them with loans and development projects intended to benefit the Chinese more than the intended recipients.

At his first stop of the tour in India, Pompeo and Defense Secretary Mark Esper had stepped up the administration’s anti-China message by playing on Indian suspicions about the Chinese to shore up a regional front against Beijing in the Indo-Pacific.

Just hours before the meetings in New Delhi began, the Trump administration notified Congress of plans for a $2.37 billion sale of Harpoon missile systems to Taiwan--the second major arms sale in two weeks to the democratic island that Beijing regards as a renegade province. China angrily reacted by announcing sanctions on U.S. defense contractors.