By Louis Charbonneau
UNITED NATIONS, Jan 20 (Reuters) - U.N. Secretary-General Ban Ki-moon said on Monday that there were heated discussions under way regarding this week's planned peace conference on Syria after the Syrian opposition threatened to pull out over a U.N. invitation for Iran to attend.
"Intensive and urgent discussions are underway and I'll have more to say about the situation later in the day," Ban told the U.N. Security Council about the Syria peace talks scheduled to begin on Jan 22.
"For the moment, let me just appeal again to all involved to keep the needs of the Syrian people foremost in mind," Ban told the 15-nation council during a meeting on the situation in the Middle East.
An unexpected last-minute U.N. invitation for Iran to attend a peace conference on Syria in Montreux, Switzerland this week threw the talks into doubt, with the Syrian opposition saying it would pull out unless Ban withdraws his offer.
Iran and Russia are the main foreign backers of Syrian President Bashar al-Assad and Tehran's presence has been one of the most contentious issues looming over the first talks attended by both Assad's government and opponents, set to start on Wednesday.
Several Western diplomats told Reuters on condition of anonymity that Ban's decision to invite Iran appeared to have been made hastily and his advisers were now scrambling to prevent a collapse of the conference on Syria's nearly three-year civil war.
The United Nations did not have an immediate response when queried about the allegation. British U.N. Ambassador Mark Lyall Grant told reporters before the Security Council meeting that Iran must explicitly and publicly embrace a plan for a political transition in Syria that was agreed in June 2012 at an international conference in Geneva if it was to attend the so-called "Geneva 2" talks.
The United States went a step further, saying it expects Ban to withdraw his invitation to Iran to attend Geneva 2 unless Tehran fully supports the June 2012 agreement on creating a transitional government for Syria - which Washington says would be without Assad.
But Russian U.N. Ambassador Vitaly Churkin disputed suggestions that the decision to invite Iran was made hastily.
Asked if Ban had consulted Russia and the United States in advance of announcing the invitation, Churkin told reporters: "Of course, everybody was consulted." He added that it would be "a big mistake" if the Syrian opposition boycotted the talks.
(Reporting by Louis Charbonneau; Editing by Chizu Nomiyama and Sofina Mirza-Reid)