“It is regrettable that Iran has yet to reach agreement with the IAEA on a plan to resolve all outstanding issues,” Haq quoted Ban as saying.

Media reported on Thursday that the International Atomic Energy Agency’ report on the Iranian nuclear problem contains information that Tehran has increased its capacity to enrich uranium at the Fordo underground site by at least 30 percent.

Haq said the secretary general emphasized that “there can only be a diplomatic and negotiated solution to the Iranian nuclear issue which should be pursued through a reciprocal, step-by-step process.”

That process “must include measures by Iran aimed at building international confidence in the exclusively peaceful nature of its nuclear program,” he said.

This week, Ban was in Tehran, where he attended a summit of the Non-Aligned Movement and held a number of bilateral meetings.

The West accuses Iran, which is under a few sets of UN Security sanctions, of pursuing a secret nuclear weapons program, while Tehran says it needs nuclear power solely for electricity generation.