Syrian activists have dismissed a decree from President Bashar al-Assad to allow opposition parties after decades of Baath party rule.
The move was an attempt to divert attention from the violent repression of protests, an activist told the BBC.
Reports from Hama say an army assault on the city has left dozens of civilians dead.
US Secretary of State Hillary Clinton said the Syrian government was responsible for more than 2,000 deaths.
Human rights groups estimate that more than 1,600 civilians have been killed since anti-government protests began in March.
At least 150 people have been killed since Sunday, mainly in Hama, the rights groups say, as the military intensifies its efforts to quell dissent.
On Thursday, President Bashar al-Assad issued a decree authorising a multi-party system, Syria's state news agency Sana said.
Mr Assad's ruling Baath party has enjoyed a monopoly on power since 1963. Ending the system of one-party rule has been a key demand of pro-democracy protesters.
The government adopted a draft law to this effect on 24 July, but the new decree gives it immediate effect.
An activist who fled Hama on Wednesday dismissed the president's move as an attempt to divert attention from what was happening in his city and other places in Syria.
"Well, this is too late for this right now, after killing so many people and invading cities and burning buildings and burning houses, raping people and arresting people and putting people in jail, what this kind of rule going to make for us now?" he told the BBC. "It's too late."
French Foreign Minister Alain Juppe also dismissed the move.
"This is almost a provocation. What we want is an end to the violence against the civilian population which is only defending its rights," Mr Juppe told French radio.
International criticism of Syria has been mounting since the UN Security Council adopted a statement on Wednesday condemning the government of President Assad for "widespread violations of human rights and the use of force against civilians".
Mrs Clinton repeated an earlier statement that the United States believed Mr Assad had lost legitimacy in Syria.
"We've seen the Assad regime continue and intensify its assault against its own people this week," she said on Thursday.
"We think to date the government is responsible for the deaths of more than 2,000 people of all ages."
She added that the US and its allies were working to apply more pressure on Syria beyond the addition of more individuals to a sanctions blacklist.
President Dmitry Medvedev of Russia, long an ally of Syria, said Mr Assad would "face a sad fate" unless he urgently carried out reforms and reconciled with the opposition.
And EU states extended their sanctions against Syria, adding more names to a list including President Assad and 34 other people as well as firms linked to the military. They stopped short of targeting the oil industry and banks, however.
'Artillery and snipers'
Dozens of people are believed to have been killed in a five-day military assault on Hama, with residents saying on Thursday that tanks have shot their way into Assi (Orontes) Square, in the centre of the city of 800,000 people.
Activists said as many as 30 more people were killed in Hama late on Wednesday, after Ramadan prayers.
One resident who escaped the city on Wednesday told the BBC it looked "exactly like a battlefield... like a Gaza Strip kind of city. Like some villages in Iraq when the US army invaded it. That's how it looks like".
He said artillery was firing at buildings and snipers were shooting at anyone they saw on the streets.
Many people had left the city, he said, but for those left, food and medicine were running low.
Communication with the city is all but completely cut off, as are water and electricity, correspondents say.
Anti-government protests began in March, inspired by the successful uprisings in Tunisia and Egypt, and soon spread to many cities across the country.
Protesters have vowed to rally every evening during the holy month of Ramadan, after nightly prayers.
Mr Assad blames the current violence on "armed criminal gangs" backed by unspecified foreign powers.