Syrian President Bashar al-Assad on Wednesday offered to hold multi-party elections within four months, while his troops assaulted city districts held by rebels trying to oust him.

In Homs, an explosion hit an oil pipeline feeding a refinery, sending smoke billowing into the sky, witnesses said. The blast was near a district under attack by the army.

Under world pressure to end a crackdown that has cost at least 6,000 lives, Assad promised a referendum in two weeks' time on a new constitution leading to elections within 90 days.

Opposition figures spurned the offer and Assad made clear he was still intent on crushing the uprising with tanks and troops. The military unleashed a new offensive in Hama, a city with a bloody history of resistance to Assad's father, Hafez al-Assad, firing at residential neighbourhoods with anti-aircraft guns mounted on armored vehicles, opposition activists said.

Artillery also shelled parts of Homs for the 13th day in a row. In Damascus, troops backed by armor swept into the Barzeh district, searching houses and making arrests, witnesses said.

International efforts to halt the carnage have stuttered.
France said it was negotiating a new UN Security Council resolution on Syria with Russia, Assad's ally and main arms supplier, and also wanted to create humanitarian corridors to ease the plight of civilians caught up in the violence.

"The idea of humanitarian corridors that I previously proposed to allow NGOs to reach the zones where there are scandalous massacres should be discussed at the Security Council," Foreign Minister Alain Juppe said on French radio.

It follows a February 4 veto by Russia and China of a draft Security Council resolution that backed an Arab League call for Assad to quit.

Russian Foreign Minister Sergei said he would hear Juppe's views, but added: "If the plan is to use the Security Council and United Nations to adopt some language to help legitimise regime change, then I'm afraid international law does not allow this and we cannot support such an approach." The referendum promise signaled that Assad wants to win the struggle on his own terms, rather than step down, as the United States, its European allies, Turkey and the Arab League demand. According to state media, the draft constitution to be put to a vote on February 26 would establish a multi-party system in Syria, under Baath Party rule since 1963. Parliamentary elections would follow within 90 days of its approval.

It would allow the president to be elected for two terms of seven years. Assad's late father Hafez al-Assad was president for 29 years and was succeeded by his son when he died in 2000.