Foreign Minister Ali Akbar Velayati of Iran and Secretary-General Javier Perez de Cuellar Tuesday held the first round of peace talks on implementing a cease-fire in the Iran-Iraq war.

Velayati met for almost 90 minutes with Perez de Cuellar and then told reporters, "We had very constructive and fruitful talks about the implementation of Resolution 598."He said he would meet the U.N. secretary-general this evening for a second round of talks.

Tariq Aziz, the Iraqi foreign minister, was to arrive in New York this afternoon. The secretary-general was to hold indirect talks with both ministers on Wednesday.

As Velayati arrived at U.N. headquarters, he condemned the latest Iraqi offensive and said Iraq was jeopardizing peace efforts by using outlawed chemical weapons.

Perez de Cuellar said that in today's talks with Velayati, he planned to discuss a cease-fire, troop withdrawal, prisoner exchange, formal peace talks and a U.N. peace plan. The substantive talks had been set to being Wednesday.

U.N. officials said Perez de Cuellar was aided by senior political, military and legal officers. The secretary-general said Monday he is optimistic a truce date can be set within 10 days.

Iran announced July 18 that it accepted Resolution 598, the year-old Security Council resolution calling for a cease-fire in the nearly 8-year-old war. Iraq previously accepted the resolution.

Since Friday, Iraq has captured Iranian territory and prisoners in a series of attacks but has said it did not intend to keep the land. Iraq has said it intended to take the prisoners to improve its bargaining position in cease-fire talks.

"They have intensified the war on the front ... in the last few hours they have attacked some cities and invaded our border," Velayati said today.

He said Iraqi officials declared Monday that their forces would withdraw from Iran by midnight. However, he said, Iraq invaded two northwestern cities "and still the war is going on very seriously and they have used chemical weapons on a large scale."