We condemn killings and massacre in Syria, whether it is security forces being killed or people and the opposition, Iranian President Mahmoud Ahmadinejad said, according to excerpts of an interview with CNN reported in Farsi by the website of Iran's state broadcaster on Saturday.

"We have a clear formula for Syria and that is for all sides to sit together and reach an understanding... therefore these killings cannot solve any problems and in the long term it will lead to a deadlock," he added.

Ahmadinejad's comments, the strongest so far from an Iranian official against President Bashar al-Assad's regime, come as Damascus presses a crackdown on nationwide protests that has killed more than 3,000 people since March 15, most of them civilians, according to the United Nations.

"When people are being killed, it paves the way for more quarrels... There should be no foreign interference (in Syria)," Ahmadinejad was quoted as saying.

"America's stance will not help. There should be no foreign intervention. All should help for understanding to prevail in Syria," Ahmadinejad said.

Washington has repeatedly called for the UN Security Council to impose sanctions on the Damascus regime and was strongly critical of vetoes by China and Russia earlier this month of even a watered-down draft threatening "targeted measures."

Iran has been concerned about the possible collapse of its principal Middle East ally and had previously avoided speaking out against the regime's deadly crackdown.

It has accused its traditional foes Israel and the United States of stirring up trouble in Syria.

Since the protests erupted, Tehran has maintained that the issue should be resolved "through dialogue and not violence."

On August 24, Ahmadinejad called on the Syrian government to find a "solution" with the protesters, as violence only "serves the interests of the Zionists."

In late August, Foreign Minister Ali Akbar Salehi said that Damascus should recognise the "legitimate demands" of its people.

In early September, Ahmadinejad said Tehran was ready to host a meeting of Islamic nations to help its ally Syria solve its political crisis.

Turkish Prime Minister Recep Tayyip Erdogan warned Iran in mid-September "not to spoil" the Syrian leadership.

"I cannot say there has been tension with Iran but we warned them (the Iranians) that 'the Assad administration is getting spoiled with your encouragement,'" Erdogan said.

Tehran has made maintaining good relations with Ankara a priority in recent years, and has considered Turkey an ally for its refusal to implement Western sanctions imposed over its controversial nuclear programme.

But in recent months Tehran has criticised Ankara over its agreement to host an early-warning radar as part of NATO's missile defence system. Tehran says the system is aimed at protecting Iran's arch-foe Israel.

The European Union has accused Iran of assisting Syria in its crackdown on anti-government protests, a charge Tehran has rejected as "baseless."

In late August, the EU named the Al-Quds force, the covert operations arm of the elite Revolutionary Guards, on a new list of those under sanctions for their suspected role in quelling the protests.

The European Union accused the force of providing "technical assistance, equipment and support to the Syrian security services to repress civilian protest movements."