U.N. Secretary-General Ban Ki-moon plans to tell Iran's leaders on the sidelines of a summit of nonaligned nations that the human rights situation in the country is critical.

U.N. associate spokesman Farhan Haq told reporters Tuesday that the U.N. chief will also convey the world's concerns on Iran's nuclear program, the Syria crisis and terrorism.

The U.N. announced last week that Ban would attend the summit of the 120-member Nonaligned Movement despite strong opposition from Israel, the U.S. and Jewish groups. Haq said he was heading to Tehran on Tuesday.

Since the announcement, human rights groups have urged the secretary-general to raise human rights concerns during his expected meetings with Iran's supreme leader and president.

The nonaligned bloc is second in members only to the U.N. General Assembly.