Buford Yates pleaded guilty to fraud and conspiracy in the federal court, saying he was instructed by supervisors to inflate WorldCom's earnings by misreporting expenses.

Yates is the second WorldCom executive who pleaded guilty after David Myers, ex-controller of the company, pleaded guilty in September to securities fraud, saying he was instructed by "senior management" to falsify ledgers.

WorldCom's Chief Financial Officer Scott Sullivan, however, has maintained his innocence. But analysts say Sullivan is under increasing pressure to cooperate with investigators after the actions taken by Yates and Myers.

The WorldCom's financial scandal was exposed to the public in June this year. The total financial misstatements is more than 7 billion US dollars, according to officials of the company which is now under bankruptcy protection.