WASHINGTON - The Bush administration said Wednesday the Philippines' president has not done enough to deal with security forces under her command who are involved in political killings.

Gloria Macapagal Arroyo did win praise for recent efforts to stop the murders. But a State Department official said Arroyo bore ultimate responsibility for the security forces' actions and the increasing attacks on people speaking out against the government.

Rights groups estimate that more than 830 activists have been killed since 2001, when Arroyo became president.

At a Senate hearing, the deputy assistant secretary of state for East Asia was asked whether Arroyo's actions had been sufficient.

"Until these numbers come drastically down though, I don't think you can determine that it's enough," Eric John told a Senate Foreign Relations subcommittee. "As the ultimate authority in the chain of command, she has to take the steps to solve any involvement by members of the security forces."

The issue is a delicate one for the administration. The U.S. depends on Manila in the fight against Islamic militants in the region who are linked to al-Qaida. The U.S. is the Philippines' closest military ally and provides crucial training and intelligence support for Philippine military offensives against extremists.

This week, the largest left-wing group in the Philippines urged the United States to stop military aid to the Philippines because of the killings of activists.

At the Senate hearing, Sen. Barbara Boxer asked John whether the U.S. should link the military aid to improvement in the country's human rights record. "It's really important that we do not have blood on our hands in this country," said Boxer, D-Calif.

John said the administration believes such action would hurt U.S. efforts to influence change in the Philippines.

Human rights leaders from the Philippines described the situation in their country. Bishop Eliezer Pascua said murder victims include reporters, lawyers, doctors, teachers, students and priests. Everyone, he said in his testimony, is afraid.

"I admit that I have that fear," said Pascua, general secretary of the United Church of Christ in the Philippines. "You can all imagine the chilling effect among the people."

Arroyo's government has denied allegations by a U.N. human rights expert and its own fact-finding commission that soldiers were behind most of the killings of activists since 2001. Arroyo's office says the government is determined to uphold the rule of law.

Military officials have accused activists of links to communist rebels, who have waged a 38-year-old rural-based insurgency.