The UN nuclear agency's trip to Iran was not as "good" as its chief inspector described this week, with real pressure now on Tehran for the next visit later this month, diplomats and analysts said. International Atomic Energy Agency chief inspector Herman Nackaerts's comment at Vienna airport on Wednesday that he had a "good trip" was "off the cuff" and "not meant to be a substantive comment," one diplomat said. "There is no indication that Iran offered substantive cooperation in terms of answering the IAEA's questions," agreed another envoy. "Iran seemed focused on modalities rather than substance." During their three-day visit from Sunday to Tuesday, the six-member IAEA team held talks with Iranian officials, but "not all" those whom they had wanted to meet, the first diplomat said. In addition, they did not visit any sites mentioned in a damning November report in which the IAEA said it suspected Iran "has carried out activities relevant to the development of a nuclear device". Iranian Foreign Minister Ali Akbar Salehi's comments to the Fars state news agency that Tehran was "ready to facilitate such visits if they had wanted to" was also disputed by diplomats to the Vienna-based IAEA. The Iranians "quite cleverly stonewalled for three days," one said. That the trip achieved so little was no huge surprise, with experts and diplomats stressing that Nackaerts going to Tehran was a step in the right direction, particularly given the spike in tensions since November's report. But more will be expected from the February 21-22 visit, which will be a closely watched test of Iran's readiness to engage with the international community, just as Western powers ramp up ever-tougher sanctions. "It's possible that Iran gives some additional information to the agency at the next meeting," said Peter Crail, nonproliferation analyst at the Arms Control Association in Washington. "But significant progress is unlikely to happen until Iran decides it can come clean on its past work on a nuclear warhead," Crail told AFP. "At some point Iran is going to have to give the agency access to personnel and sites involved in the programmes the IAEA is concerned about." The second Vienna diplomat said it was unclear if the next visit would achieve much, however. "I don't think the agency has assurances that the next meeting will be more substantive, I think that is still to be decided ... The outcome seems to be 'let's talk some more'," said the diplomat, from a Western power. If there is no progress "it won't look good for Iran," the first envoy said, with the IAEA expected to prepare a report on its cooperation with the Islamic republic for a board meeting of the agency on March 5. "I think the agency is under no illusions that the member states and the international community are going to be shining a very high-beam spotlight onto this visit," the first diplomat said. "The question is, on the next trip, with the Iranians knowing that there are certain areas and places where the agency would like to go, is that on the cards? At this point I don't think the agency knows -- yet." Mark Hibbs, analyst at the Carnegie Endowment for International Peace, said that the IAEA "needs a major breakthrough with Iran to prevent the conflict from escalating at the board in March". "They will need to get firm commitments from Iran that it will cooperate. That may need to be negotiated still. At this point a conditional maybe won't suffice," Hibbs told AFP. What won't suffice, diplomats say, is some sort of "work plan" similar to the one agreed with Iran in 2007 that included a series of steps towards resolving the IAEA's concerns. "We would like to avoid being in a work plan situation," said one, adding that his country wanted to "avoid becoming hostage to a box-ticking exercise."