William Hague, the British foreign minister, has announced that he would meet with Syrian opposition representatives in London next week in an intensification of contact with opponents of President Bashar al-Assad.
The Syrian opposition members would also meet senior aides of David Cameron, the UK prime minister, at his Downing Street office, the foreign ministry said on Friday.
It said that Frances Guy, the former British ambassador to Lebanon, had been appointed to co-ordinate relations with the Syrian opposition.
The delegation would include members of the opposition Syrian National Council and the National Co-ordination Committee for Democratic Change, in meetings expected to take place on Monday, a Foreign Office source said.
"We have been having regular contacts with a variety of figures in the Syrian opposition for several months. We are now intensifying these," the Foreign Office said.
The announcement came as the Arab league said that Syria had agreed "in principle" to allow an Arab League observer mission into the country.
Walid al-Muallem, Syria's foreign minister, sent a letter to Nabil Elaraby, the Arab League chief, requesting changes to the league's proposal which entailed sending 500 observers to Damascus to try to help end the bloodshed, the pan-Arab bloc said.
The 22-member bloc voted at an extraordinary meeting in Cairo on Saturday to suspend Syria until Assad implemented the deal to end the crackdown, which has left at least 3,500 people dead since March, according to UN figures.
Activists reported that at least 17 people were killed on Friday by security forces, including two children, as fresh protests broke across the country calling on nations to expel Syrian ambassadors from their countries.
The Free Syrian Army were reported to have killed three members of the security forces on Friday.
In another development, Alain Juppe, the French foreign minister, called on the UN Security Council to act against Assad's government, saying the time has come to strengthen sanctions against Syria.
"We must continue to exert pressure," Juppe said at a joint news conference with Ahmet Davutoglu, the Turkish foreign minister, in Turkey's capital.
"If there's no response to the latest attempt of the Arab League, which has Turkey's support, then certain measures must be taken"
- Ahmet Davutoglu, the Turkish foreign minister
Davutoglu also increased pressure on Syria, saying that "if there's no response to the latest attempt of the Arab League, which has Turkey's support, then certain measures must be taken".
Vladimir Putin, the Russian prime minister, called for restraint over the crisis.
"We are calling for restraint and caution. This is our position," Putin told a news conference, a day after his foreign minister had likened the situation in Syria to a civil war.
Hillary Clinton, the US secretary of state, warned on Friday of the possibility of a civil war in Syria that either is
directed or influenced by Syrian army defectors.
"I think there could be a civil war with a very determined and well-armed and eventually well-financed opposition that is, if not directed by, certainly influenced by defectors from the army," Clinton told the US network NBC.
"We're already seeing that, something that we hate to see because we are in favour of a peaceful ... protest and non-violent opposition."
On Friday, activists said that Syrian troops had shelled two northern villages overnight after an attack by army defectors on forces loyal to Assad, in the first report of such an incident during the eight-month uprising.
Eight villagers were injured when tank shells and heavy mortars fell for three hours on Tal Minnij and Maarshamsheh and surrounding farmland, activists told the Reuters news agency.
"Hundreds of families have left. Electricity and internet services have been cut off," said one activist who gave his first name as Raed.
Army defectors had earlier attacked a building housing security forces near army depots in the Wadi al-Deif area on the edge of the town of Maarat al-Numaan, 290km north of Damascus, the activists said.
In-depth coverage of escalating violence across Syria
The town, on the Damascus-Aleppo highway, has seen regular street protests demanding Assad's removal and raids by security forces to put down the demonstrations.
In the last few weeks, residents say a growing number of army defectors have been defending Maarat al-Numaan and attacking army patrols and roadblocks.
The authorities blame the violence on foreign-backed armed groups who they say have killed more than 1,100 soldiers and police.
Syria's official news agency said troops carried out a "qualitative operation" in the region, arresting 58 wanted people and seizing rifles and bomb detonators.
The agency said eight "of the most wanted terrorists" were arrested on Thursday in the central city of Homs, where tanks have been deployed.