United Nations Secretary-General Javier Perez de Cuellar says talks due to begin on Thursday on ending the Gulf War could take years.

"It all depends on the political will of the parties," he said in an interview with Le Monde published Wednesday. "If they really want to resolve the problem, it could be done in some months. Otherwise it could last years, and then I would have to name a personal representative to follow the negotiations."Talks involving Perez de Cuellar and the foreign ministers of Iran and Iraq are due to begin in Geneva on Thursday following Saturday's U.N.-observed cease-fire. Among the problems Perez de Cuellar listed were the demarcation of the Shatt al-Arab waterway, which forms part of the border between Iran and Iraq, troop withdrawals, and how to form the body that is to decide which country was responsible for starting the eight-year war.

Iranian Foreign Minister Ali Akbar Velayati delayed his travel to Geneva, but an advance delegation arrived.

Iranian Foreign Ministry officials declined to say why Velayati had not arrived as scheduled on Wednesday but noted that Iraqi Foreign Minister Tareq Aziz had not yet arrived either.

Ali Shams Ardekani, a senior Iranian Foreign Ministry adviser, told Reuters that Velayati would arrive on Thursday.

Meanwhile, a U.N. team of chemical weapons experts has backed Iran's claim that Iraq dropped mustard gas on an Iranian city this month in a raid that came after both sides had accepted a U.N. cease-fire resolution.

In a note attached to the report Tuesday, Perez de Cuellar said the bomb attack violated provisions in the 1925 Geneva Convention on the use of poison gases.

There were no reported deaths in the Aug. 2 attack on the city of Oshnaviyah, which is a few miles from the northeast corner of Iraq, though Iran said 2,680 people were injured. Baghdad denied responsibility for the raid.

Security Council President Li Luye of China held talks about the report with other members of the council Tuesday, said U.N. spokeswoman Nadia Younes.

Members of the U.N. team were Dr. Erik Dahlgren of Sweden's Defense Research Establishment; Col. Ulrich Imobersteg, former chief of Switzerland's nuclear, biological and chemical defense force; and Dr. A.N.P. van Heijst, former director of the Dutch National Poison Control Center.