Allegations that a group of US marines raped a woman during shore leave after a joint training exercise with Philippine forces has riled public opinion in this former US colony.
The case could prove awkward for President Gloria Arroyo-Macapagal, a close US ally who is struggling to quash accusations of electoral fraud.
Philippine officials stress that the Visiting Forces Agreement, signed between the two countries after the closure of US military bases in 1992, has provisions to cover such cases. But lawmakers have questioned Mrs. Arroyo's commitment to enforcing the treaty and warned of a backlash if the marines receive kid-glove treatment.
"This is an emotional issue involving our sovereignty and our citizens, and we must take jurisdiction right away," says Sen. Richard Gordon, former governor of Subic Bay, the former US naval base where the alleged rape occurred last week.
Any immediate impact on US military training and aid for counterterrorism operations in the southern Philippines is unlikely, say observers. US trainers were sent to Mindanao in 2002 to help combat the Abu Sayyaf and other extremist groups.
But sensitive to public cries for justice, Arroyo's supporters say they want to ensure that the servicemen are tried here under the joint treaty.
District prosecutors issued subpoenas Tuesday for six US marines to appear in court later this month as part of a preliminary investigation. None have been charged yet. The six servicemen, who are based in Okinawa, Japan, are in the custody of the US Embassy, which has pledged to cooperate.
US naval investigators are conducting a separate inquiry, said embassy spokesman Matthew Lussenhop. "There is a legal framework for addressing issues like this and I don't expect that it will damage US-Philippine relations," he says.
The case revives memories of past abuses by US forces stationed in Subic Bay who were shielded from local prosecution. It comes amid a revamp in the US presence in Japan, where tensions have often erupted, most notoriously over the 1995 rape of a minor by three US servicemen.
The US trainers here have taught combat skills to Philippine troops, including special operations units, and assisted with intelligence gathering. The result has been a successful clampdown on Abu Sayyaf operations in Basilan, their former stronghold, though the group continues to pose a serious threat. It was blamed for a 2004 ferry bombing that killed more than 100 people. Officials say Abu Sayyaf has regrouped elsewhere in Mindanao and adopted bombmaking skills from Jemaah Islamiyah, the Indonesian-based group.
Strong cultural and historical ties have made the Philippines something of an exception to the rule that the US has steadily lost global support. Opinion polls are often supportive of US policy.
But Filipinos say the plight of powerless victims sacrificed to realpolitik resonates strongly in a nation that identifies with the underdog. The same emotional response, coupled with an anti-Arroyo bandwagon that has already tried unsuccessfully to impeach the president, could prove a potent mix.
"If there is a strong perception that the Visiting Force Agreement is not being followed, this could make the public think that Filipinos are at a disadvantage," warns Sen. Rodolfo Biazon, a former Arroyo ally who has called for her resignation.
According to local officials, the six marines met their alleged victim at a bar in Subic Bay and took her for a ride in a hired van. Witnesses saw the van pull over and leave a woman in her underwear on the sidewalk. The woman, whom local media identified as a college graduate on vacation, was taken to a hospital. She later told police that she had been raped during the drive.
Under questioning, the van's driver alleged that at least one marine had taken advantage of the woman. The others were said to have cheered during the alleged rape, said Congresswoman Milagros Magsaysay, who spoke to the victim and investigators. Rape is punishable here by a life sentence or even death.
Arroyo's opponents have staged almost daily protests outside the US Embassy. Local media have followed the case and played up inflammatory comments by politicians, including one senator who called the US servicemen "sexual terrorists."
But the demonstrations have remained small. "I don't feel that the Americans are trying to hide anything from us. They just want to get to the bottom of this, as we do," says Ms. Magsaysay.