Both Cambodia and China denied such reports. Cambodian Defence Minister Tea Banh said that the country’s constitution strictly forbade hosting foreign troops in its territory. Time will tell whether China will establish such a base in Cambodia.

The more interesting question is the potential strategic implications of a Chinese base in southern Cambodia. US Deputy Secretary of State Wendy Sherman reiterated US concerns over the ‘construction of such facilities’. While the United States has not elaborated on the threat that a Chinese naval base at Ream may pose, most analysts argue that it would increase the PLAN’s ability to operate in the disputed waters of the South China Sea.

But a base at Ream would not significantly improve the Chinese navy and air force’s ability to operate in the South China Sea. Chinese naval vessels and aircraft stationed in Hainan and southern China are well within the range of all the islands claimed by China in the Paracel and Spratly islands. Chinese aircraft have flown in large numbers as far south as Malaysia. In June 2021, Malaysia reported that 16 Chinese aircraft flying in formation had violated its air space.

For Chinese navy vessels operating from Hainan and southern China, a base at Ream is even less important. China has built at least 20 artificial islands in the South China Sea — many of them with infrastructure far more sophisticated than the Ream base.

In March 2022, US Indo-Pacific Commander Admiral John C Aquilino said that China had fully militarised at least three islands in the South China Sea. He claimed China had deployed anti-ship missiles, air defence missiles, fighter jets, lasers and anti-jamming equipment on these islands. These militarised islands are within the protective range of aircraft and air defence missiles based in southern China.

But while Ream is not vital for Chinese power in the South China Sea, it has strategic importance for Vietnam. Vietnam’s east coast faces the Chinese island of Hainan where the PLAN’s south fleet is based. China could blockade the east coast of Vietnam quickly, including its main naval base at Cam Ranh Bay.

Because Cambodia shares both land and sea borders with Vietnam, a Chinese naval presence in Ream — less than 100 miles from the Vietnamese southern coast — would be useful to China. A Chinese base would allow China to blockade the southern Vietnamese coast in a matter of hours. The combination of Chinese naval forces in Hainan and Ream would effectively seal off Vietnam from the sea. The Vietnamese army fought well during China’s 1979 invasion — inflicting heavy casualties on the People’s Liberation Army — but in a conflict over the South China Sea, the Vietnamese navy and air force would be no match for the Chinese.

Vietnam has been trying for decades to contain Chinese influence in Cambodia and Laos. But China’s overwhelming economic power has made these efforts difficult. In the north, Vietnam shares a land border with China and in the west, with Laos and Cambodia. Laos and Cambodia are highly dependent on China for trade and investment and have become close diplomatic allies of Beijing.

Rather than just focussing on Cambodia, the United States should look at ways to support Vietnam more actively. There have been years-long rumours that some in the Vietnamese elite were considering allowing the US navy to return to its old Vietnam War-era base at Cam Ranh Bay. US naval ships have visited the base in recent years.

The legacy of the Vietnam War makes it difficult for a proud nation such as Vietnam to allow a US base to be established in its territory. But if China does open a naval base at Ream, this may change.

Loro Horta is a diplomat and scholar from Timor-Leste. He has served as Timor-Leste’s ambassador to Cuba and counselor at the Timor-Leste embassy in Beijing.