US President Barack Obama has said he is pushing for diplomacy with the new Iranian government over its suspect nuclear programme to bring about "broader peace" in the region.
Speaking at the UN General Assembly in New York on Tuesday, Obama said that Iran had been a major source of instability for too long and seeks to resolve the nuclear issue peacefully.
"The roadblocks may prove to be too great, but I firmly believe the diplomatic path must be tested," he said, adding that he was charging US Secretary of State John Kerry with pursuing progress on the nuclear issue with Iran, in coordination with five other world powers.
Obama was set to have "an encounter" with Iranian President Hassan Rouhani, but Iran said that the meeting was "too complicated for Iranians to do at this point".
Meanwhile, French President Francois Hollande said at the meeting that he has decided to engage in a "direct and open dialogue" with the Iranian president, but stated that he was firm on the issue of nuclear proliferation.
Obama also demanded that the world should take action on Syria, reiterating his threat of force against Syrian President Bashar al-Assad's government.
"It is an insult to human reason - and to the legitimacy of this institution - to suggest that anyone other than the regime carried out this attack," he said.
Speaking in front of the UNGA earlier, UN Secretary-General Ban Ki-moon called on major powers to stop sending weapons to all sides in Syria, as he opened the annual UN General Assembly summit.
The UN chief also called on Assad and the Syrian opposition - and "all those in this hall with influence over them" - to work immediately to arrange a second Geneva conference aimed at reaching a political solution to the crisis that has wracked Syria for more than two years.
"Military victory is an illusion. The only answer is a political settlement," he said.
Ban said the response to last month's "heinous use of chemical weapons" outside Damascus "has created diplomatic momentum - the first signs of unity in far too long".
His appeal comes as the United States and Russia haggle over the language in a UN Security Council resolution meant to seal an agreement for Assad to give up chemical weapons.
Kerry was to meet his Russian counterpart Sergei Lavrov later in the day. Russia is the main supporter of Assad, while the rebels receive support from Western nations and Sunni Arab monarchies.
A top Russian diplomat said that the resolution would include the article of the UN Charter that allows the use of force or sanctions.