VIENNA (AP) — A senior U. N. nuclear expert today announced plans to revisit Tehran soon after a “ good trip,” indicating progress on his team’s quest to probe suspicions that the Islamic Republic is secretly working on an atomic arms program.

The announcement from mission leader Herman Nackaerts came shortly after his group landed at Vienna airport after three days of discussions with Iranian officials in Tehran.

While Nackaerts gave no details on what the International Atomic Energy Agency experts had achieved, diplomats had said before their departure that their main focus was to break Iranian resistance to talking about the weapons program allegations.

“ We had three days of intensive discussions about all our priorities, and we are committed to resolve all the outstanding issues,” Nackaerts told reporters. “And the Iranians said they are committed, too.

“But, of course, there’s still a lot of work to be done,” he said. “ So we have planned another trip in the very near future.”

Asked how the visit was, he replied, “we had a good trip.”

Diplomats familiar with IAEA strategy told The Associated Press before the trip that the agency delegation was unlikely to settle for vague promises or complicated plans that could further stall their probe. Nackaerts’ announcement that a new visit would soon take place — plus his praise of a “ good trip” — therefore suggested that he was coming back to Vienna with some progress made.

Any progress on the issue would be significant. Iran has refused to discuss the alleged weapons experiments for more than three years, saying they are based on “fabricated documents” provided by a “few arrogant countries” — a phrase authorities in Iran often use to refer to the United States and its allies.