The United States has said the Ream Naval Base, located off Cambodia's southern coast, could give China a key strategic position in the Gulf of Thailand near the disputed South China Sea, which Beijing claims almost in its entirety.

Cambodian senior officials have repeatedly denied that the base is for use by any single foreign power, following US media reports in 2022 saying that the new facilities at Ream were being built for the exclusive use of the Chinese navy.

Military representatives from various nations attended a ceremony on Saturday marking the inauguration of the renovated Ream base, with Cambodia rolling out the red carpet for a delegation from China's People's Liberation Army.

Prime Minister Hun Manet hailed the opening of the upgraded port at the event, where Cambodian and Chinese flags were flown.

"We hold the live inauguration today because we want both Cambodian people, and people and all forces around the world to stop casting doubt about it," he said in a speech.

"From today Cambodia will welcome all friends to hold joint exercises in the Ream base. We have nothing to hide at all," he added.

Hun Manet promised that the new and improved facility would not be for Beijing's "exclusive" use and that ships from other countries would be allowed to dock.

The ceremony also featured remarks from Cao Qingfeng, a Chinese senior military official, who said the port symbolised the "iron-clad friendship" between the two nations and would "inject new momentum into regional security".

He added that the base would be used for joint military exercises, including the annual Golden Dragon drills in May.

- Staunch allies -

Cambodia has long been one of China's staunchest allies in Southeast Asia, and Beijing has extended its influence over Phnom Penh in recent years.

Under former leader Hun Sen -- Prime Minister Hun Manet's father -- China poured billions of dollars into infrastructure investments, while Washington's relationship with Phnom Penh has deteriorated in recent years.

Hun Manet said Saturday that Chinese President Xi Jinping will visit Cambodia this month, confirming previously reported plans of such a trip.

Beijing has since 2022 been contributing to a revamp of the Ream Naval Base, which was originally built partly using US funds.

Western concerns about the base go back as far as 2019, when The Wall Street Journal reported on a secret draft deal allowing China to dock warships there.

In late 2023, Chinese warships first docked at the 363-metre (1,190-foot) pier, located on Cambodia's sole coastline in the south of the country between Thailand and Vietnam.

Cambodia is also expected to receive two warships from China to improve its defence capabilities.

In December, a US warship docked in nearby Sihanoukville in the first American military port call in eight years.

That was followed in February by the visit of a senior US army commander to Cambodia, featuring a meeting with Hun Manet in a trip intended to "expand bilateral defence ties".

Last month, Cambodia said a Japanese warship would be the first to dock at the Ream base.