UN Secretary-General Ban Ki-moon on Friday sought to salvage efforts to broker a truce in Syria, admitting that the process was "in crisis" because the Syrian government and opposition were both unwilling to compromise.

UN-Arab League special envoy Lakhdar Brahimi would travel to Iran, Ban said, to try to break the deadlock in the negotiations. He was due to touch down in Tehran on Sunday.

As a key regional player, Ban Said that Iran "can play an important role, including impressing upon the Syrian authorities to come to the Geneva conference in a more constructive way."

Iran is considered a key regional ally for Syrian President Bashar al-Assad. Ban had invited Tehran to attend the last round of international talks in Geneva, but was forced to rescind the offer under pressure from the US and the Syrian opposition.

The public protests against Assad that ultimately escalated into civil war began in earnest precisely three years ago, on March 15, 2011.

Appeal to US, Russia - election looms over talks

Speaking at the UN in New York, Ban also urged the US and Russia to take "clear steps to re-energize the political process" in the Syrian negotiations. The appeal came amid an unusually tense atmosphere between Washington and Moscow, owing to Crimea's controversial weekend referendum on joining the Russian Federation.

In Syria, the government is planning presidential elections, currently due before July. Mediator Brahimi told the General Assembly that such a vote "will slam the door to the Geneva negotiations for the foreseeable future."

Assad is widely expected to seek another seven-year term, but has not yet announced his candidacy. Syria's parliament on Thursday approved a new electoral law designed to prevent many opposition candidates from running.

"I very much doubt that any of the opposition groups that are strongly opposed to the present government, inside or outside of the country, will consider that negotiations may continue if presidential elections are scheduled in May or June," Brahimi said in his closed-door address, according to the transcript released afterwards.

US State Department spokeswoman Marie Harf said on Friday that an Assad re-election campaign "would be offensive and disgusting," considering the past three years of violence.

"The planning of any national election at this time, I think, would be an affront to the Geneva talks, would only make more clear that the regime is intent on undermining prospects for a political solution," Harf told reporters.

FM Moallem undergoes heart surgery

Meanwhile, Syrian state media reported that Foreign Minister Walid al-Moallem, a close confidant of Assad, underwent successful heart surgery in a Lebanese hospital on Friday. State news agency SANA described the procedure as "pre-planned cardiac surgery."

Moallem, 73, was ambassador to Washington for nine years starting in 1990; he took up the foreign minister's post in 2006. He also led the Syrian government delegation at the last round of UN-hosted talks in Geneva.

msh/crh (AFP, AP, Reuters)