Updated 1:46 PM ET
VIENNA - A senior U.N. nuclear inspector spoke Wednesday of a "good trip" to Tehran and the agency said his team will return to Iran's capital in late February, indicating progress on attempts to investigate suspicions that Iran is secretly working on nuclear weapons.
The International Atomic Energy Agency's announcement of a renewed mission to Tehran Feb. 21 came just hours after the return of a senior team and word from the team leader that a new trip was planned "in the very near future."
Neither the IAEA's formal statement nor mission Head Herman Nackaerts gave details on what the agency's experts had achieved. But any headway would be significant after more than three years of Iranian stonewalling on attempts to investigate the allegations.
Nackaerts spoke of "three days of intensive discussions," telling reporters at Vienna airport that -- while "there still is a lot of work to be done" -- the IAEA is "committed to resolve all the outstanding issues, and the Iranians said they are committed too."
Asked how the visit was, he replied, "we had a good trip."
Like Nackaerts, the IAEA statement also suggested some progress by indicating that the Iranian side did not reject the agency's requests out of hand, as it has in the past on the issue of weapons work. It said the agency team "explained its concerns and identified its priorities, which focus on the clarification of possible military dimensions to Iran's nuclear program."
"The IAEA also discussed with Iran the topics and initial steps to be taken, as well as associated modalities," said the statement, citing IAEA chief Yukiya Amano as saying "it remains essential to make progress."
The visit, it said, will last for two days.
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.
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.
Alluding to such fears, U.N. Secretary-General Ban Ki-moon on Wednesday told Israel that the international standoff over Iran's suspect nuclear program must be resolved peacefully.
At a news conference with Israel's prime minister in Jerusalem, Ban urged the Iranians to prove their nuclear program is for peaceful purposes. When asked whether he fears an Israeli attack, he said "there is no alternative to a peaceful resolution of these issues."
While Iran has publicly belittled efforts to force it to compromise on its nuclear programs, sanctions and other international pressure appear to have left their mark, as reflected by the indications that the IAEA mission made some progress.