A U.S.-based organization that observed Pakistan's elections said Friday that TV news coverage was biased but it had no evidence to substantiate charges of mass vote rigging leveled by former prime minister Benazir Bhutto.

"It is our opinion that the safeguards in the system would make tampering on on a scale sufficient to affect the overall nationwide result difficult," said a statement by the National Democratic Institute.The Washington-based institute sent a 40-member delegation to observe last Wednesday's National Assembly elections. It said it came to the conclusion election workers apparently were impartial and effective.

The statement said, however, that the election was not without problems. It complained of biased news coverage by the state-run television and said corruption charges filed against Bhutto and members of her administration "complicated the pre-election atmosphere."

Bhutto, whose government was dismissed in August, has charged the Islamic Democratic Alliance's win was achieved as a result of "gross rigging." She alleged that ballot boxes had been switched after the votes were cast.

Bhutto has agreed that her Pakistan People's Party will still contest Saturday's elections.