PHNOM PENH (REUTERS) - The US Federal Bureau of Investigation (FBI) will set up an office at Cambodia's national police headquarters to help track down American criminals, at a time when Washington is seeking to repair strained relations with a close ally of China.

The office will serve to support Cambodian police in efforts to arrest American fugitives and to fight terrorism, police spokesman Chhay Kim Khoeun said on Tuesday (Oct 13).

"Before, we cooperated on a case-by-case basis and now we are having an office to work with the objective to work fast,"Chhay Kim Khoeun told Reuters.

Chhay Kim Khoeun said he did not know about the timeframe for when the office would be established.

In an email statement to Reuters, the US Embassy in Phnom Penh declined to comment on the FBI office but said the two institutions had an established relationship.

"A joint FBI-Cambodian National Police task force established to fight crimes against children, money laundering, and financial crime is now operational. Our law enforcement cooperation makes both our countries safer," it said.

An agreement was made last year to create the task force, which would also address organised crime, money laundering and locate international fugitives, the embassy said.

Ties with the United States have been frosty in recent years, with Cambodia's government angered by Washington's criticism of the dissolution of the main opposition party and arrest of rival politicians and activists.

Last week, the Pentagon expressed concern about the razing of a US-funded Cambodian navy tactical headquarters, which Prime Minister Hun Sen said was for renovations.

Cambodia has repeatedly denied reports there was a secret deal with China, its biggest economic and diplomatic ally, to place forces at the base.