Leaders from emerging powers on Wednesday expressed their opposition to threat of military action against Tehran, amid US and Israeli warnings they will not tolerate a nuclear-armed Iran.

"We are concerned about threats of military action as well as unilateral sanctions," leaders from Brazil, Russia, India, China and South Africa said at the end of a two-day summit.

The group, which includes two veto-wielding members of the United Nations Security Council -- China and Russia -- urged the standoff over Iran's nuclear programme to be solved by "political and diplomatic means."

The comments come just days after US President Barack Obama reiterated his pledge that he would consider all options in preventing Iran's nuclear programme from being weaponised.

"I have made the position of the United States of America clear: Iran must not get a nuclear weapon. This is not a danger that can be contained," he said on a recent visit to Israel.

Tehran says the programme for peaceful purposes.

The BRICS leaders also expressed "deep concern" over the deteriorating security and humanitarian situation in Syria, while tacitly opposing Western calls for Bashar al-Assad to be ousted.

They called for a "Syrian-led political process" to achieve peace through dialogue "that meets the legitimate aspirations of all sections of Syrian society and respect for Syrian independence."

The group also expressed its "opposition to any further militarization of the conflict."

But in an apparent about-face for Russia and China, the BRICS also called for humanitarian workers to be allowed to have unimpeded access to the country.

Syria has so far refused to allow UN and aid groups into opposition areas, a stance Russia has backed as part of its support for Assad.

"We call upon all parties to allow and facilitate immediate, safe, full and unimpeded access to humanitarian organisations to all in need of assistance," the statement said.

"We urge all parties to ensure the safety of humanitarian workers."