US aircraft carrier arrived on Monday in Vietnam for the first time since the end of the Vietnam war, dramatically underscoring the growing strategic ties between the former foes at a time when China’s regional influence is rising.

The grey and imposing silhouette of the USS Carl Vinson could be seen on Monday morning from the cliff tops just outside the central Vietnamese city of Da Nang, where the 103,000-tonne carrier and two other US ships begin a five-day visit.

The arrival of the Vinson marks the biggest US military presence in Vietnam since 1975 – but it also illustrates Hanoi’s complex and evolving relationship with Beijing over the disputed South China Sea.

Vietnamese Foreign Ministry spokeswoman Le Thi Thu Hang said the visit would “continue to promote bilateral relations within the framework of the two countries’ comprehensive partnership and contribute to maintaining peace, stability, security, cooperation and development in the region.”

Vietnamese envoys had been working for months to ease the concerns of Beijing over the visit and the prospect of broader security cooperation between Hanoi and Washington, according to diplomats and others familiar with the talks.

US carriers frequently ply the South China Sea in a rising pattern of naval deployments, and are now routinely shadowed by Chinese naval vessels, naval officers in the region say.

China’s rapid construction and build-up of the land it holds in the disputed Spratly Islands group has alarmed Vietnam and other regional governments as it seeks to enforce its claims to much of the disputed waterway, through which some US$3 trillion in trade passes each year.

While some Chinese commentators have used the Vinson’s presence to demand an even greater Chinese military build-up in the South China Sea, official reaction from Beijing has been relatively muted since the stop was announced in January.

That announcement came during a two-day visit to Hanoi by US Defence Secretary James Mattis and followed months of back room military diplomacy between Hanoi and the Pentagon.

Le Hong Hiep, a research fellow at the Singapore-based ISEAS-Yusof Ishak Institute said that the Carl Vinson’s visit would likely irritate China, but that Beijing would not take it too seriously.

“They understand well the strategic rationale behind the rapprochement between Vietnam and the US, which was largely driven by China’s growing assertiveness in the South China Sea,” he said. “However, China also knows that Vietnam is unlikely to side with the US militarily to challenge China.”