MONTREUX, Switzerland - United Nations Secretary-General Ban Ki-moon sparred with Syria's Foreign Minister on Wednesday when he tried to cut short the minister's speech to an international peace conference.

Walid al-Moualem had already spoken for more than twice the 10-minute limit at the talks in Switzerland when Ban interrupted to urge him to bring his comments to a conclusion, but the intervention proved fruitless.

"You spoke for 25 minutes," Moualem shot back. "I came here 12 hours in the airplane. I need a few minutes to finish my speech."

"Can you just wrap up in one or two minutes?" Ban persisted.

"No I can't promise you. I must finish my speech," came the reply from Moualem, who used his address to accuse rebels of disembowelling pregnant women, raping them dead or alive and bombing mosques.

He also told participants that it was up to Syrians to choose their leader, not foreign powers who are calling on President Bashar al-Assad to step down, and pointedly accused Turkey and Gulf Arab states of fuelling the violence in Syria.

Ban said he would have to give other speakers more time if Moualem did not stop, an appeal which also failed to impress the Syrian minister.

"You live in New York, I live in Syria. I have the right to give the Syrian version here in this hall. This is my right."

Ten minutes later, with no end in sight, Ban tried again.

"I will finish one sentence," Moualem told him.

"One sentence or two. Just to keep your promise, one sentence," the U.N. Secretary-General said.

"Syria always keeps its promise," Moualem answered, before wrapping up his hard-hitting, 35-minute address about a minute later.

At the start of the talks, aimed at ending Syria's near three-year conflict, Ban had urged all participants to "refrain from language that could undermine chances of success at the conference", and to stick rigorously to their allocated time.

"I regret to tell you that from the beginning, this constructive mood and rules which I set and you agreed has been broken ... I hope that this will not be repeated.

"Please refrain from making any accusation from any specific countries and refrain from inflammatory remarks which must unnecessarily provoke the participating countries in good faith. I really appeal to all of you," Ban told the participants.