OLONGAPO CITY, Philippines (REUTERS) - A Philippine trial court on Monday entered a plea of not guilty on behalf of a United States Marine accused of killing of a transgender Filipino, in a case that could test the strength of security ties between the two allies.

The Marine, Joseph Scott Pemberton, who is being held at a US facility at the main Philippine army base, was charged with the murder of Jeffrey Laude, who was found dead on Oct 11 in a hotel in Olongapo City, outside a former US naval base.

A handcuffed Pemberton appeared in court, and sat quietly, flanked by US security officers. He did not say a word when the murder charges were read by a clerk, and left after signing some court documents.

The court entered a plea of not guilty for him.

Pre-trial hearings were set this week to mark evidence and list the witnesses to be called by each side.

"Finally the trial started," Laude's sister, Marilou, told journalists. "Finally, we can now seek justice for our brother."

The Laude family was not interested in an out-of-court settlement, said Harry Roque, a private prosecution lawyer.

Another lawyer, Virgie Suarez, complained the media were not allowed into the courtroom. "The situation inside was very intimidating," she said, adding that Pemberton was escorted by 16 American security personnel.

The marathon trial is expected to begin next month because the court has only one year to resolve the case, under a 1998 pact between the Philippines and the United States that sets out the rules for the treatment of erring servicemen.

Pemberton's arraignment in December was postponed after his lawyers appealed to the justice department against the decision to indict him, but that appeal was thrown out.

A few anti-US activists gathered outside the court to demand justice for Laude. Dozens of news cameramen and photographers also waited for Pemberton, who was brought to court in a convoy of heavily-tinted SUVs.