President Obama and Iran\'s president are both to attend a U.N. General Assembly luncheon Tuesday, but the White House insisted no exchange was scheduled. Obama is to participate in the annual luncheon of world leaders hosted by U.N. Secretary-General Ban Ki-Moon, the White House said Monday evening. Iranian President Hassan Rouhani, who has engaged in several weeks of charm diplomacy suggesting a desire to improve relations with the United States and the West in general, is also to participate in the 1:15 p.m. luncheon in the U.N. Conference Building, between the General Assembly building and the Secretariat. That luncheon -- in a large room with big glass windows facing New York\'s majestic East River on one side and an oil canvas mural depicting a phoenix rising from its ashes hanging in the front -- is widely seen as an opportunity for the two leaders to have at least a brief exchange. An Obama-Rouhani exchange would mark the first meeting between a U.S. and Iranian leader since President Jimmy Carter met with Shah Mohammad Reza Pahlavi in December 1977, 14 months before Iran\'s Islamic Revolution. The United States broke diplomatic relations with Iran April 7, 1980. Switzerland represents U.S. interests in Tehran while Pakistan represents Iranian interests in Washington. The White House repeated Monday Obama was \"open to engagement\" with Rouhani. \"He\'s exchanged letters with Rouhani,\" deputy national security adviser Ben Rhodes told reporters traveling with the president to New York. \"We simply have not had a meeting scheduled,\" he said. Rhodes said Obama has expressed his willingness since his 2007 pre-election campaign \"to engage the leaders of Iran in pursuit of an agreement\" in which Iran proves its nuclear program is exclusively for peaceful purposes. Washington and U.S. allies allege Iran is well along toward developing a nuclear weapon, but Tehran insists its nuclear activities are only to produce electricity and for medical research. \"Clearly, this is going to take time,\" Rhodes said. \"You\'re not going to solve all the issues with Iran in any one meeting or encounter. But what we\'re signaling is that we\'re open to engagement generally toward resolving this issue. \"We don\'t have anything scheduled between the president and President Rouhani,\" he added. When asked if the leaders might shake hands purely by \"happenstance,\" Rhodes said, \"I don\'t think that anything would happen by happenstance on a relationship and an issue that is this important.\" When asked if an invitation had been made to meet or shake hands, Rhodes said, \"We have nothing scheduled with the Iranians at this point.\" Obama is to address the General Assembly around 10 a.m., shortly after Ban addresses the body. Rouhani -- a Shiite Muslim cleric, lawyer, academic and former diplomat -- is to address the assembly around 5 p.m., some 4 hours after the luncheon. Western diplomats predict Rouhani\'s speech will be conciliatory and include an important gesture, such an acknowledgment of the Holocaust -- a sharp contrast to the angry, Holocaust-denying diatribes of his predecessor, Mahmoud Ahmadinejad. Rouhani is to be accompanied at the General Assembly by Ciamak Morsadegh, Iran\'s only Jewish member of Parliament. Whether or not the two presidents meet, U.S. Secretary of State John Kerry is to meet his Iranian counterpart, Mohammad Javad Zarif, Thursday in the first face-to-face foreign minister exchange between the two countries since 2007 and the first official meeting on that level since 2000. Zarif, who got his doctorate in international law and policy from the University of Denver, is to join nuclear talks in New York between the United States and five other world powers -- Russia, China, Britain, France and Germany. It was not immediately clear if Kerry and Zarif would break off from the group and meet one-on-one.