UNITED NATIONS - The chief war crimes prosecutor for the United Nations said yesterday she hoped to learn by the end of the year whether she should investigate the presidential assassination that sparked the 1994 genocide in Rwanda.

Carla del Ponte, who heads the prosecution office of the International Criminal Tribunal for Rwanda, told a news conference in New York it was not clear she had the authority to probe the death of President Juvenal Habyarimana, who had ruled Rwanda since the early 1970s. The United Nations set up the tribunal to try people accused of genocide or crimes against humanity, but Ms. del Ponte said Mr. Habyarimana's death did not necessarily fall into either of those categories.

"To kill the president is murder, but it is not under our jurisdiction for prima facie investigation," she said. Talk of investigating the assassination was rekindled earlier this year when the National Post uncovered a confidential UN document that raised new questions about the unsolved murder.

The document refers to three informants who told tribunal investigators in 1997 that previous assumptions about who killed President Habyarimana in a missile attack on his plane had been wrong. Instead of being the victim of a plot by Hutu extremists, they suggested the president was killed by mainly Tutsi rebels on the order of General Paul Kagame, now Rwanda's president. Because the assassination sparked the killings of at least 500,000 Tutsis, Rwandan Hutus now charged with inciting the massacres believe confirmation of the informants' claims will help blunt the cases against them.

Though everything contained in the document about the assassination has already appeared in exclusive Post reports, newspaper accounts cannot serve as evidence in this instance. The work of a French judge looking into the plane attack for the families of three French crew members will help Ms. del Ponte determine whether the assassination is a matter for her tribunal. If the judge concludes "the plane crash of the former president was an act relating to the genocide organization, we have jurisdiction," said Ms. del Ponte. "We will have a result in some months ... I hope before the end of the year."

She spoke as judges of the Rwanda tribunal, which is based in Arusha, Tanzania, handed down their first rejection of a recent slew of applications to have the assassination investigated. The court refused the request of Gratien Kabiligi, a former brigadier general in the Rwandan army, to have the assassination investigated. Judges said his lawyer had failed to prove the president's death was linked to the charges against him. It also ruled no "legal basis" for such an investigation had been established.

The rejection did not deter Joseph Nzirorera, a former Rwandan politician also charged in the genocide, from calling on the court to order the prosecution office to probe the assassination. Two other Hutus charged in the genocide have made similar calls. The court also heard Rwanda make the surprising statement that the confidential document, which rekindled the debate about the assassination, should be released. "We are not opposing disclosure of the report," Martin Ngoga, Rwanda's court representative, told journalists, "because we believe its continued concealment gives it a credibility it doesn't have."