Rev Nadim Nassar warned military involvement against the Syrian government would inevitably draw in Russia, as the foreign secretary summoned various foreign ministers for fresh talks at the weekend.
Speaking on Premier's News Hour programme, Rev Nassar said: "Military victory is not possible in Syria. The only thing possible is to sit around the table and find a way. We could have done it three years ago."
Boris Johnson on Thursday said dialogue with Russia over the conflict in Syria had reached a dead end and he requested his US, French and German counterparts join him on Sunday to explore "more kinetic options."
He also said: "Most people, I think, are now changing their minds about this and they are thinking 'We can't let this go on for ever, we can't just see Aleppo pulverised in this way, we have to do something'."
Fighting involving Syrian government and Russia forces against opposition groups has killed at least 358 civilians in Aleppo since a US and Russian-brokered ceasefire broke down on September 19th, the Britain-based Syrian Observatory for Human Rights has said.
Rev Nassar said he hoped the meeting of foreign ministers on Sunday would help stem the flow of weapons into Syria, explaining: "We need to keep talking.
"Every dialogue regarding Syria is helpful however faint the hope is. We need to reduce more and more the arms that go to Syria."
Prime Minister Theresa May's official spokeswoman said: "There is no change in the Government's position with regard to [military action].
"But I think the Prime Minister would weigh up very carefully any options that were put forward and the potential consequences of those.
"At the moment, our focus is on bringing together partners, as I think the Foreign Secretary outlined at the [Commons foreign affairs] committee. We will be gathering leaders in the UK this weekend to talk about what more we can do."
Click here to listen to Nadim Nassar speaking with Premier's Alex Williams:
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