East Timor rejected China's proposal to build a radar on its territory after concerns it would be used for intelligence purposes, according to WikiLeaks, a report said Tuesday.

US diplomatic cables, published in the Sydney Morning Herald, show China approached East Timor in December 2007 about building the surveillance facility, free of charge, on the country's north coast.

The Chinese said it would help East Timor in its fight against illegal fishing, according to the leaked cables.

But East Timor's deputy prime minister Jose Luis Guterres was worried that the radar would be used to extend China's intelligence capabilities further into Southeast Asia.

"The only catch was that the facilities were manned by Chinese technicians," Guterres reportedly told the US embassy, expressing "concerns that the radar could be used for purposes other than those touted by the Chinese".

"They could instead be used to extend China's radar-based intelligence perimeter deep into Southeast Asia," he said.

The waters of the Wetar Strait separate East Timor's northeast coast from Indonesia's Pulau Wetar island and are reportedly used by US Navy vessels including nuclear submarines in transit between the Pacific and Indian oceans.

The cables show US diplomats in Dili reported that East Timor President Jose Ramos-Horta had "repeatedly and explicitly" affirmed that the nation's "strong preference" was to cooperate with its democratic partners on defence and security.

By this, Ramos-Horta was referring to Australia, Portugal, the United States and Japan, the report said.