Foreign Secretary William Hague has issued a fresh condemnation of Russia's decision to veto a United Nations resolution on Syria and said the international body could be sidelined in efforts to support the opposition movement.
Although the UK would not offer "lethal support" to the rebels, he warned that other countries would step up the supply of arms following the failure of the Security Council to approve a resolution threatening sanctions against president Bashar Assad's regime.
The Security Council will consider a further resolution today to extend the mandate of the observer mission for what Mr Hague said would be a "final" 30-day period.
He said Russia would regret its use of the veto, claiming Moscow used a "spurious argument" and warning that its interests in the Middle East would suffer long-term harm as a result of its stance.
China lined up behind Russia in blocking the resolution and Mr Hague said the Security Council was "failing in its responsibilities" as a result of the stalemate.
"We will all be doing more outside the Security Council and intensifying our work to support the Syrian opposition, to give humanitarian aid, outside the work of the Security Council," he told BBC Radio 4's Today programme.
"We do not give lethal support, but I have no doubt there will be other countries that will give greater lethal support to the Syrian opposition in these circumstances."
Mr Hague said he did not expect the UK to be involved in arming the opposition to Assad's regime.
"I don't rule out any option for the future because we can't foresee how it will develop, but it's never been our policy in any of the conflicts in the Middle East to send lethal assistance to any of the parties involved.
"I do think in this case that the Syrian opposition are receiving arms, that's very evident from their ability to make military progress against a powerfully equipped regime."
He added that the UK would prefer an arms embargo on everyone in Syria, including an end to Russia's supply of weapons to Assad's forces.
Interpreting Moscow's position, Mr Hague said: "They don't want to see what happens in Syria as another victory of any kind for Western foreign policy."
But he added: "I think they will regret it. I think the situation will now deteriorate further, sharply, probably to the disadvantage of the Assad regime and to the disadvantage of Russian interests in Syria and the Middle East in the longer term."
The limited resolution now before the Security Council would result in "final 30-day rollover" of the UN mission to monitor special envoy Kofi Annan's peace plan.
Mr Hague said: "It is of course a mission in great doubt ... but I think its actual withdrawal would be seen as another bleak moment in what is happening in Syria.
"So we think it is right to give a final opportunity to say this mission will still be there for 30 days but if there is no political process or implementation of the Annan plan after 30 days, well, then let's not pretend it can achieve anything."