Mohammad Khazaee, Iran’s ambassador to the United Nations, took questions this week at an unusual forum hosted by the Asia Society. Critics argued that the forum was simply an opportunity for Iranian propaganda, but as moderator of the discussion, I thought it made an important, if somewhat discouraging, point: There isn’t yet sufficient trust on either side for a broad agreement.

The discussion took place a week before the next negotiating session between Iran and the P5+1 group of nations, scheduled for Feb. 26 in Kazakhstan. Khazaee’s stance might be described as forthrightly ambiguous. That is, he suggested a deal can be imagined in principle but cautioned that the environment isn’t conducive for making it happen in practice.

For example, when I asked whether Iran was ready to endorse a framework for resolving the nuclear issue that might involve caps on Iranian enrichment and export of existing stockpiles of enriched material, Khazaee answered “yes and no,” and then explained what he meant.

The “yes” part was that Iran was prepared to be flexible on such details as the level at which it enriched uranium and the size of the stockpile it maintained, so long as its basic right to enrichment was recognized. But the “no” involved the atmosphere in which such an agreement might be reached. “The point is … the mistrust that exists between the two countries. As soon as one side says something … [the other side] says there is a hidden agenda.”

Khazaee elaborated on a statement last week by Iran’s supreme leader, Ali Khamenei, that he won’t negotiate under pressure. The Iranian ambassador clarified that removal of sanctions wasn’t a precondition for negotiations and that there was no “red line” against diplomacy with the United States and the other P5+1 countries. But he insisted: “More pressure can only beget more distrust, leading Iran, in turn, to lose hope in a negotiated settlement.”

Thomas Pickering, a former senior U.S. diplomat who took part in the discussion, saw in Khazaee’s comments a positive sign that the supreme leader was still open to talks and prepared to be “reasonable,” as Khazaee quoted him saying. But Pickering argued that because of the deep suspicions on both sides, any U.S.-Iranian discussions should begin with “small steps” rather than a grand bargain.

It’s always useful when officials answer questions in a public forum, and I suspect that many in the audience came away encouraged that progress can be made in the negotiations. But Khazaee is a diplomat, and as his boss, the supreme leader, said bluntly in his statement last week: “I’m not a diplomat, I’m a revolutionary.”

The problem is that it’s hard to negotiate agreements with revolutionaries. That may be especially true if they feel there is a gun pointed at their head. A diplomat might compromise, but a revolutionary could well say: Go ahead, pull the trigger.