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President Barack Obama is expected to build on diplomatic opportunities and signal his willingness to engage with the new Iranian government if Tehran makes nuclear concessions long sought by the US and Western allies.
Obama, in a planned address to the United Nations General Assembly today, also will call on UN Security Council members to approve a resolution that would mandate consequences for Syria if it fails to cooperate with a plan to turn its chemical weapons stockpiles over to the international community.
The president's address will be closely watched for signs that he may meet later in the day with Iranian President Hasan Rouhani, a moderate cleric who has been making friendly gestures toward the US in recent weeks.
Even a brief encounter would be significant given that the leaders of the US and Iran haven't had face-to-face contact in more than 30 years.
US officials say no meeting was planned, though they hadn't ruled out the possibility that one might be added. The most likely opportunity appeared to be at a UN leaders' lunch today.
Rouhani was scheduled to address the UN General Assembly later today.
The possibility of a thaw in relations with Iran was expected to factor heavily in Obama's address to the UN.
