Britain announced Wednesday it would begin direct talks with military figures in Syria's armed opposition groups, as Prime Minister David Cameron called for a new international approach to ending the conflict.
In a statement to parliament, Foreign Secretary William Hague said Britain would not supply weapons to the rebels and said officials would stress to the opposition groups the importance of respecting human rights.
Hague said opposition groups were playing an "increasingly influential role" in Syria as the conflict worsens.
"I have therefore now authorised my officials to have direct contact with an even wider range of representatives, including military figures in the armed opposition," he said.
"This will help us to understand better the situation in Syria and the relationship between political and armed opposition groups so we can properly support political transition."
All the contacts would take place outside Syria, Hague said.
In an interview with Al-Arabiya television on Tuesday, Cameron had said he would support giving safe passage to President Bashar al-Assad if it meant ending the near 20 months of bloodshed in Syria, and he repeated this on Wednesday.
"I would like to see President Assad face full international justice for the appalling crimes he has meted out on his people," he told the BBC, but added: "What we want to see is transition in Syria. We want Assad to go."
Cameron was on Wednesday visiting a refugee camp for Syrians in northern Jordan, where he said he would press the newly elected US President Barack Obama to work on a stronger international approach to the crisis.
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"Right now the international community has to recognise that what we've done is not enough," Cameron told the BBC from Zaatari refugee camp while lies not far from the Syrian border.
"We need more pressure at the United Nations, more help for the refugees, more help for the opposition, more action to turn the screw on this dreadful regime.
"And that is my priority with the newly elected president."
Cameron used the visit, which comes at the end of a three-day tour of the United Arab Emirates, Saudi Arabia and Jordan, to announce an extra £14 million (17.5 million euros, $22.5 million) in aid for Syrian refugees.
This brings the total British humanitarian aid in the crisis to £53.5 million since the start of 2012.
Britain's main goal is to encourage Syria's many opposition groups, some of which are meeting in Doha this week, to unite around a single vision for a democratic and stable Syria.
British special envoy Jon Wilks, who is attending the Doha talks, has so far been in contact with political groups, human rights activists and civil society groups but has now been tasked with widening the net.
Hague said all contacts with armed groups would comply with Britain's stated policy of only supplying non-lethal support, and with an EU arms embargo on Syria.
"In all contacts my officials will stress the importance of respecting human rights and international human rights norms, rejecting extremism and terrorism, and working towards peaceful political transition," he added.
"British contacts with military elements of the Syrian armed opposition will be limited to a political dialogue including working towards and inclusive political transition."