Syrian opposition leaders will meet Foreign Secretary William Hague to discuss what role the UK could play in bringing about a political solution to the conflict in Syria.
Monzer Akbik of the Syrian National Coalition (SNC) said other countries would form a "coalition of the willing" to launch strikes against Assad even without the UK's involvement.
He told BBC2's Newsnight that the international community had a duty to "take measures in order to paralyse the ability of the war machine of the regime to kill".
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One of the attackers who murdered a priest in a French church during morning mass in Normandy has been named by prosecutors.
Father Jacques Hamel has been described as man who dedicated his life to his parishioners and still regularly led mass, even at 86.
Rain will spread southeastwards through N. Ireland, Wales and England overnight.