WASHINGTON (AFP) - A senior US law enforcement agent has provided a major breakthrough in a Navy corruption scandal by agreeing to plead guilty to taking bribes, The Washington Post reported on Thursday.

The case has already implicated half a dozen navy officers and could taint more.

John B. Beliveau II, a supervisory special agent with the Naval Criminal Investigative Service, will enter a guilty plea next week in San Diego, the Post said, quoting court records and his attorney.

Beliveau was arrested in September and charged with helping Singapore-based Navy contractor Glenn Defence Marine Asia dodge multiple criminal investigations by leaking inside information about NCIS probes in exchange for prostitutes, cash and other favors.

The Post said that two people involved in the case, speaking on the condition of anonymity, claim Beliveau had agreed to share information with federal prosecutors about his extensive relationship with Leonard Glenn Francis - president of Glenn Defence Marine and a co-defendant in the case - as well as others involved in the investigation.

Francis, known in navy circles as "Fat Leonard", is a Malaysian citizen and a well-known figure to scores of Navy officers. Their ships depended on his firm for logistical support during Asian port visits. He has pleaded not guilty.

Beliveau's plea would mark a big step for investigators. They are trying to figure out the scope of the alleged corruption involved in the awarding and administering of lucrative Navy contracts for port services in Asia.

Besides Beliveau, two navy commanders have been arrested and charged with taking bribes.

Two captains have been suspended or reassigned. And Two admirals working in navy intelligence had their access to classified materials suspended while investigators probe their possible involvement.