U.N. Secretary-General Javier Perez de Cuellar called on Iran and Iraq during a one-day break at their peace talks Saturday to move faster and try to dispel a climate of mutual "distrust."

Perez de Cuellar lauded the Iranian and Iraqi foreign ministers for being "highly polite" during the first two days of talks Thursday and Friday, but said work must be accelerated at the U.N.-sponsored talks aimed at transforming an Aug. 20 cease-fire into permanent peace.Participants said privately that a major problem involved rights of navigation in the strategic Shatt al Arab estuary between the two nations. The waterway is Iraq's only access to the Persian Gulf.

Iranian Foreign Minister Ali Akbar Velayati demanded a return to a 1975 accord that gives each nation the right to use half of the waterway. Iraq wants to control it completely and Iraqi Foreign Minister Tariq Aziz rejected the demand.

Perez de Cuellar asked both sides to consider Saturday "a day of reflection" before resuming talks Sunday, and U.N. spokesman Francois Giuliani said there were no contacts with the two sides.

The secretary-general spoke with reporters Saturday before holding meetings with Moroccan and Polisario guerrilla delegates on the Western Sahara conflict and with Palestine Liberation Organization chairman Yasser Arafat.

Perez de Cuellar was asked about any progress on a timetable for implementing U.N. Security Council Resolution 598 on the gulf war cease-fire, repatriation of prisoners and a political settlement.

"We are working, but I have to admit at rather a slow pace because you know we work in an atmosphere which is understandably an atmosphere of distrust so far," he replied.

"I hope that we are slowly going to build up a better climate for the talks, but so far I must say both interlocutors have been highly polite and they have listened to each other with patience and I hope with understanding."

Perez de Cuellar said his time was limited, and he wanted a timetable fixed before leaving for Lisbon for a meeting next Thursday with Portuguese President Mario Soares.

"They (Iran and Iraq) know I have other commitments," he said.

Voluntary repatriation of an estimated 80,000 and 100,000 by the International Committee of the Red Cross is the first measure called for by Resolution 598.

Then follow even trickier issues as part of a settlement, such as defining the international frontier, Shatt al Arab freedom of navigation, and determining responsibility for the nearly 8-year-old war which is estimated to have killed or wounded as many as one million people.