AMMAN/BEIRUT (Reuters) - Syrian opposition leaders and the West have scorned a new offer by President Bashar al-Assad to hold multi-party elections, as his troops mounted more attacks on rebel-held areas.
Assad promised a referendum in two weeks' time on a new constitution leading to elections within 90 days, but made clear he still planned to crush the uprising against him by force.
The military unleashed a new offensive in Hama, a city with a bloody history of resistance to Assad's late father Hafez al-Assad, firing at residential neighborhoods with anti-aircraft guns mounted on armored vehicles, opposition activists said.
Artillery shelled parts of Homs for the 13th day in a row. In Damascus, troops swept into the Barzeh district, searching houses and making arrests, witnesses said.
France said it was negotiating a new U.N. Security Council resolution on Syria with Russia, Assad's ally and main arms supplier, and 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.
He said a U.N. General Assembly vote on Thursday on a non-binding resolution on Syria would be "symbolic." 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 Lavrov said he would listen to Juppe, but added: "If the plan is to use the Security Council and United Nations to adopt some language to help legitimize regime change, then I'm afraid international law does not allow this and we cannot support such an approach."
Lavrov said later on Wednesday: "If leading members of the international community demand regime change as a condition for everything else, then we are convinced ... this is the way to a full civil war with unforeseeable consequences."
Diplomats said Arab delegations had rejected proposed Russian amendments which would weaken the Assembly resolution.
The Arab League wants a joint U.N.-Arab peacekeeping force to be deployed in Syria and has adopted a resolution that would allow its members to arm Syrian rebels.
Libya's interim leader, Mustafa Abdel Jalil, said "our brothers" in the exiled opposition Syrian National Council (SNC) would be allowed to open an office in Tripoli. "We support the Syrian people and their aspirations," he said.
Council members re-elected Burhan Ghalioun as its head at a meeting in the Qatari capital Doha on Wednesday.
The Council is hoping to gain international standing through a "Friends of Syria" meeting on February 24 in Tunisia, which like Libya has seen the overthrow of an authoritarian leader in the last 12 months. Council Secretary General Wael Merza said 74 countries and organizations would be at the meeting.
Western powers are keen to see Assad go but are wary of intervening in a country at the heart of a volatile region.
The United States, its European allies, Turkey and the Arab League demand that Assad step down.
Syrian state media said on Wednesday a 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.
But new parties could not be based on a religion or regional interests, which appeared to exclude the outlawed Muslim Brotherhood or autonomy-seeking Kurdish parties.
Melhem al-Droubi, a member of the SNC and the Muslim Brotherhood, told Reuters that Assad must resign now.
"The truth is that Bashar al-Assad has increased the killing and slaughter in Syria. He has lost his legitimacy and we aren't interested in his rotten constitutions, old or new," he said.
The United States also dismissed the referendum plan.
"Promises of reforms have been usually followed by increase in brutality and have never been delivered upon by this regime since the beginning of peaceful demonstrations in Syria," White House spokesman Jay Carney said.
"The Assad regime's days are numbered."
Assistant Secretary of State for International Security and Nonproliferation Thomas Countryman said the United States was "deeply concerned" about arms transfers from Iran to Syria.
He said Iran was supplying weapons that could be used against protesters, as was Russia. He added the United States was concerned about the fate of "tens of thousands" of shoulder-fired anti-aircraft missiles Syria is believed to possess.
The Syrian leader dismisses the revolt as the work of terrorists backed by a conspiracy of enemy nations.
Thousands of civilians have been killed since the uprising began in March, inspired by other Arab revolts. The government says it has lost more than 2,000 soldiers and police dead.
Syrian forces battered rebel-held areas on Wednesday, although official media restrictions made it impossible to verify the accounts provided by activists.
In Homs, an explosion hit an oil pipeline feeding a refinery, witnesses said. The Syrian Observatory for Human Rights reported two people killed in Homs' Baba Amr district in a new wave of shelling in the evening.
Hundreds of people have been killed in the military's nearly two-week-old bombardment of rebel-held areas of Homs. Activists and aid groups report a growing humanitarian crisis there, with food running short and wounded people unable to get proper care.
The British-based Observatory also said five soldiers were killed in Idlib, near the Turkish border, when a homemade bomb planted by rebels hit an armored vehicle.
Also in Idlib province, two people, one of them a 12-year-old boy, were killed by gunfire from security forces in Sarmin and at least 15 wounded, it said.
Writing by Angus MacSwan in Beirut; editing by Andrew Roche