Iran's foreign minister urged delegates at a Non-Aligned Movement (NAM) developing nations summit on Sunday to oppose sanctions imposed by the West on the Islamic Republic to punish it for its nuclear activities.
Western diplomats have sought to play down the importance of NAM at the start of Iran's three-year presidency of the body set up in 1961 to counter big power domination of international relations.
However, Iran welcomed delegates from the group of 120 developing nations to the meeting it says proves that Washington has failed to isolate it from the rest of the world.
"The non-aligned (movement) must seriously oppose ... unilateral economic sanctions which have been enacted by certain countries against non-aligned countries," Foreign Minister Ali Akbar Salehi told the summit's opening session.
The West accuses Iran of seeking to develop nuclear weapons. Tehran denies this and says its nuclear research is for civilian purposes but refuses to curb its nuclear enrichment programme.
Police and security unit have flooded Tehran for the NAM meeting amid warnings to opposition activists against rekindling protests which brought millions into the streets in 2009 against the re-election of hardline President Mahmoud Ahmadinejad.
Eighty countries are participating in the summit at the level of minister or higher, Foreign Ministry spokesman Ramin Mehmanparast said, with 50 sending their heads of government.
And the expected attendance of big players including U.N. Secretary General Ban Ki-moon and Egypt's new president, Mohammad Mursi - the first Egyptian leader to visit Iran since the 1979 Islamic revolution - will give the meeting diplomatic heft.
Since the toppling of Egypt's Western-backed President Hosni Mubarak last year, non-Arab Iran has hoped for a thaw in relations with the regional power, but Cairo has appeared less eager to embrace Shi'ite Muslim Iran which is viewed with suspicion by its Sunni Gulf Arab neighbours.
"The presence of the Egyptian president in Tehran will help develop Tehran-Cairo relations," Mehmanparast told reporters.
With the Syrian crisis likely to dominate talks, Iran's support for President Bashar al-Assad, who is using heavy weaponry against an uprising that threatens to have repercussions around the region, is likely to face scrutiny.
Mehmanparast said Iran expected to consult with countries on the sidelines of the summit on a "comprehensive package" to resolve the Syria crisis.
In a possible sign of things to come, a senior official presiding over Sunday's talks, Mohammad Mehdi Akhundzadeh, indicated discussions had thrown up disagreements but that Iran and Qatar had helped to resolve differences of opinion, Fars news agency said.
The final report from meetings at official level will be finished on Tuesday and will form the basis of discussions between foreign ministers and heads of state later in the week.
Divisions within the Muslim Middle East were also evident when Tehran moved to deny media reports that it had invited Ismail Haniyeh, the leader of Hamas, the Islamist group that controls the Gaza Strip.
"From Palestine, only Mahmoud Abbas, the president of the Palestinian Authority, has been invited to Tehran for participation in this summit, and an official invitation has not been sent to any other individual," Mehr news agency quoted Mehmanparast as saying.
Tehran has declared a five-day holiday in the capital to ease traffic pressures and enhance security, which is being guaranteed by hundreds of police units.
"Police are stopping a lot of people in the streets and are standing on every corner," said a 30-year-old Tehran resident who asked not to be named. Another resident said there were unprecedented numbers of stop-and-search teams.
Conservative cleric Ahmad Khatami, in an interview published last week, warned opposition supporters against using the summit for their own aims.
An opposition group based outside the country has asked U.N. chief Ban to ask to meet opposition leaders Mirhossein Mousavi and Mehdi Karoubi who have been held under house arrest since February 2011 as the Arab Spring uprisings raged in the Middle East.