UN Chief Ban has revoked, under pressure from the United States, his invitation to Iran to take part in an international conference aimed at putting an end to the deadly conflict in Syria.

United Nations Secretary General Ban Ki-moon has revoked, under pressure from the United States, his invitation to Iran to take part in an international conference aimed at putting an end to the deadly conflict in Syria.

UN spokesman Martin Nesirky said Ban is "deeply disappointed" at Iran's statements rejecting the June 2012 Geneva communiqué.

"Given that it has chosen to remain outside that basic understanding, he has decided that the one-day Montreux gathering will proceed without Iran's participation," Nesirky added during a press briefing at the UN headquarters in New York on Monday.

The 2012 Geneva communiqué outlines measures for a transition of power in Syria, and its key demand means Syrian President Bashar al-Assad will have to step down.

Iran had insisted it would attend Geneva II without precondition set by the US or any other power.

More than 35 countries will gather in the Swiss cities of Montreux and Geneva from Wednesday for talks on finding a peaceful solution to Syria’s crisis.

On Sunday, the UN chief said Iran has been invited to the Geneva II conference. “As I have said repeatedly, I believe strongly that Iran needs to be part of the solution to the Syrian crisis,” he stated.

But the United States, Britain, Saudi Arabia and the foreign-backed Syrian opposition were strongly opposed to Iran’s participation in the event.

The US said the UN must take back its invitation unless Tehran publicly backs the 2012 roadmap to establish a transitional government in Syria, and the so-called Syrian National Council (SNC) threatened to skip the Geneva II conference entirely.

However, Russian Foreign Minister Sergei Lavrov said Iran;s absence from the talks will be “unforgivable mistake”.