The US Treasury Department this week announced it was freezing any US assets and criminalising transactions with senior defence ministry official Chau Phirun and naval commander Tea Vinh over alleged corruption linked to the Ream Naval Base.

Washington accused the pair, along with other Cambodian officials, of conspiring to inflate costs at the base to pocket the proceeds.

"Cambodia strongly deplores the long-arm jurisdiction of the United States over Cambodian officials on the basis of groundless allegations driven by geopolitical motives," the Cambodian foreign ministry said in a statement.

"The smear campaign and unilateral sanction of the United States against public figures of a sovereign state... (displays) an utter contempt for the independence of another country as well as acts as a serious interference in its domestic affairs," the statement said.

The Cambodian foreign ministry also warned that the move was "another step in the wrong direction" for ties between the two countries.

The base on the Gulf of Thailand has been a running sore in US-Cambodia relations in recent years, with Washington suspecting it is being converted for use by China.

Cambodia has been dismantling facilities at the base that were built partly with American money and played host to US exercises.

Satellite imagery taken in August showed the construction of two new buildings, likely indicating that China is pushing ahead on a new agreement, according to the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies in Washington.

Hun Sen has repeatedly denied his country would host the Chinese military at the base.

Senior US officials have warned Cambodia that hosting a Chinese base would damage relations with Washington.

China has been increasingly assertive over its extensive territorial claims in the South China Sea and the East China Sea, raising tensions with numerous Asian nations, but Cambodia has increasingly appeared as an ally.