The British Government is increasing its work with the Syrian political opposition as part of efforts to create an alternative to President Bashar al Assad's regime.
Foreign Secretary William Hague said a British diplomat met representatives of the Free Syrian Army (FSA) this week.
The UK is also to provide an extra £5m in non-lethal equipment, such as communications devices, to help activists co-ordinate efforts.
In an article in The Times, Mr Hague said: "The people of Syria cannot wait while the wheels of diplomacy turn.
"Many more people will die without urgent help. That is why we will now focus our efforts on urgent practical assistance to Syrians on the ground, while diplomacy continues."
Meanwhile, rebels retreated from the key Aleppo district of Salaheddin under heavy shelling, as a veteran Algerian diplomat was set to be named the new international envoy to Syria.
"We have staged a tactical withdrawal from Salaheddin. The district is completely empty of rebel fighters. Regime forces are now advancing into Salaheddin," said Hossam Abu Mohammed, an FSA commander.
"The fighters are withdrawing to (nearby) Sukari district, where they are preparing a counter-attack."
He added: "A large number of civilians were killed, as were some 40 rebels. Forty buildings have been flattened."
Syrian state television said: "Our special forces have cleansed Salaheddin district of terrorists."
It came as Algerian diplomat Lakhdar Brahimi, 78, is to be named as Kofi Annan's replacement as Arab League joint special envoy for Syria, according to diplomatic sources quoted by Reuters news agency.
An announcement about Mr Brahimi - who has served as a UN special envoy for Iraq, Afghanistan, Haiti and South Africa - could come as early as next week.
Mr Assad's forces have so far killed more than 15,000 people, in its effort to crush the rebellion that erupted in March 2011, some Western leaders say.
Damascus said rebels have killed several thousand members of its security forces.
Mr Annan, a former UN secretary-general, announced last week he would step down because he was unable to do his job with the UN Security Council's veto powers deadlocked over Syria.
The council united in April to approve the deployment of 300 monitors to observe a failed ceasefire as part of Mr Annan's peace plan.
But Russia and China have vetoed three other resolutions criticising Syria and threatening sanctions against Damascus.