Russia and the United States' differences on the Syrian conflict were laid bare on Sunday as Lakhdar Brahimi headed to Cairo for talks with Arab leaders on his first visit to the region as peace envoy.

Government forces meanwhile bombarded rebel positions in Aleppo, destroying a crucial water pipeline in Syria’s second city after a day of fierce clashes with rebels.

Brahimi, who last week described the Syrian bloodshed as “staggering” and the destruction “catastrophic”, was on his way to the Middle East for the first time since taking up his role as the UN-Arab League envoy.

The veteran troubleshooter took over from Kofi Annan, the former UN chief who quit the post in early August complaining of “continuous finger-pointing and name-calling” at the UN Security Council.

US Secretary of State Hillary Clinton said on Sunday that a new Security Council resolution on Syria would be pointless if it had “no teeth”, as President Bashar al-Assad would ignore it.

Speaking in Russia, Clinton said she was willing to work with Moscow on a new resolution but warned Washington would step up support to end Assad’s regime if the measure did not carry consequences.

“There is no point to passing a resolution with no teeth because we’ve seen time and time again that Assad will ignore it and keep attacking his own people,” Clinton told reporters at the end of an Asia-Pacific summit.

Russian Foreign Minister Sergei Lavrov said on Saturday after talks with Clinton that he hoped to seek Security Council approval for a peace plan agreed in June in Geneva that called for a ceasefire and political transition.

“I will continue to work with Foreign Minister Lavrov to see if we can revisit the idea of putting the Syrian transition plan that we agreed to in Geneva earlier this summer into a Security Council resolution,” Clinton said.

“But as I underscored yesterday with Foreign Minister Lavrov, that will only be effective if it includes consequences for non-compliance.”

Clinton said she hoped for progress but was “realistic” that the United States and Russia had differences on Syria.

If those differences persist, “then we will work with like-minded states to support a Syrian opposition to hasten the day when Assad falls and to help prepare Syria for a democratic future and help it get back on its feet”, she said.

The United States has said it is providing non-lethal assistance to the opposition in Syria, whose regime which has been a Moscow ally since the Cold War.

Brahimi was travelling to the Egyptian capital on Sunday for talks with Arab League leaders ahead of a trip he hopes to make to Damascus, according to his spokesman Ahmad Fawzi.

“We are working on the final details of a plan to visit Damascus and it will happen quite soon if all the details fall into place,” Fawzi told AFP.

According to UN diplomats, Brahimi has been seeking guarantees that he will get a proper meeting with Assad before he goes to Damascus.

Brahimi has said it is up to the Syrians to decide their future, echoing the position of Annan.

The Algerian former foreign minister, who took up his post on September 1, has warned that the situation across Syria is “deteriorating steadily.”

Brahimi said before taking up his post he was not confident of being able to restore peace, warning that it was a matter of ending rather than avoiding a civil war in Syria, whose conflict is 18 months old.

On the ground, government forces bombarded a central neighbourhood of Aleppo after a day of fierce clashes with rebels who tried to take the regime-controlled district, the Syrian Observatory for Human Rights said.

Several houses were destroyed in the shelling of the northern city’s Midan district, which is mostly under regime control, said the Britain-based watchdog.

Fierce battles broke out on the edge of Midan on Saturday, after rebels tried to take over the district from their stronghold in Bustan al-Basha.

A main water pipe in Bustan al-Basha was destroyed, either by air strikes or the fighting, and water shortages were reported by residents in Aleppo.

“The bombardment of Bustan al-Basha has stopped but could start up again anytime,” a resident told AFP.

According to the water department, the main water line which burst was still broken but repairs were underway.

Sunday’s violence followed a bloody day in which 135 people — 63 civilians, 33 rebels and 39 soldiers — were killed nationwide, the Britain-based Observatory reported.

As many as 38 people were killed by shelling attacks on the districts of Shaar, Halwani and Sid al-Luz on Saturday, the watchdog said. The names of 17 have been documented thus far.

Another 17 bodies were discovered in a trench in Aleppo city, while at least 11 people were killed in shelling in Tadamun and Yarmuk Palestinian camp in Damascus.