France has said that it wants the UN Security Council to set up humanitarian corridors in Syria to alleviate civilian suffering and that it is now negotiating with Russia on a new UN resolution.

However, Russian Foreign Minister Sergei Lavrov said his country, which has already joined China in vetoing two UN Security Council resolutions on Syria, could not support using the UN body to "help legitimise" regime change in Damascus.

Paris suggested in November creating a safe passage for relief organisations to get food and medicine to civilians caught up in the 11-month-old struggle to topple President Bashar al-Assad.

"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 told France Info radio.

Mr Lavrov was non-committal when asked whether Russia supports such a plan. "It's impossible to answer such questions without having language (details) in your hands," he told reporters.

Denmark's Foreign Minister Villy Søvndal earlier said the European Union was preparing a humanitarian contingency plan for Syria.

He said that the EU's message to Russian and China is that they should not be on the wrong side of history.

As pressure mounts on his regime, President Assad ordered a referendum on a new constitution on 26 February.

Reports said parliamentary elections would be held within 90 days of approval of a draft constitution.

State media claimed that the draft constitution would establish a multi-party system in Syria, which has been ruled by President Assad's Ba'ath Party for nearly half a century.

However despite this announcement, Syrian government forces launched an offensive on the city of Hama, firing on residential neighbourhoods from armoured vehicles and mobile anti-aircraft guns, opposition activists said.

Troops also shelled Sunni Muslim neighbourhoods in Homs, the 13th day of their bombardment of a city that has been at the forefront of the uprising against Mr Assad's rule.

Tanks deployed near the city of Hama are shelling the neighbourhoods of Faraya, Olailat, Bashoura and al-Hamidiya, and troops are advancing from the airport, opposition sources said.

In Damascus, Syrian forces, backed by armoured personnel carriers, stormed part of the city in the closest deployment of troops to the centre of the capital in the 11-month uprising.

Troops from the Fourth Armoured Division and Republican Guards have erected roadblocks in main streets of Barzeh neighbourhood, a residential neighbourhood north of the city centre.

Residents said the troops are looking for opposition activists and members of the rebel Free Syrian Army, which has been providing security for protests against President Assad in the district.

UN General Assembly to vote on new resolution

The United Nations General Assembly will vote tomorrow on a new resolution calling on President Assad to put a stop to deadly attacks on civilians, diplomats said.

The resolution, drawn up by Saudi Arabia and Qatar, which was given to member nations yesterday, also expresses support for the Arab League's plan to end the crackdown and calls for the naming of a UN special envoy.

The move comes after Russia and China vetoed a second Security Council resolution on the crisis in Syria on 4 February, because they said it was "unbalanced".

Russia and China are expected to oppose the new text but no one can veto resolutions in the 193-nation General Assembly, although they carry less weight.