London - On Thursday in St Petersburg, world leaders have the opportunity to break the deadlock in the UN Security Council over Syria.
The voice in the margins of the G20 meeting that needs to be heard on Syria, above all, is that of the German Chancellor Angela Merkel. She could mobilise India, Brazil, Japan and others for a very simple proposition:
"Leave aside for the moment your differences in the Security Council on who did or did not use gas in Syria. You five countries that are Permanent Members - China, Russia, the US, France and the UK - cannot agree over what military action should or should not be taken over that, but surely you can agree that all chemical weapons should be removed from Syria now and that such a process should start now under UN supervision as was done in Iraq in 1991."
If all the participants at St Petersburg could rally to forge such a consensus it would bypass the dispute over who was responsible for the gas attack - Assad or the rebels. Neither Obama nor Putin need retract a word they have said.
Obama has already said that the advice of the chiefs of staff is that military action is not time sensitive. This means he can hold open the threat. Putin has every interest in letting Assad know that he stands by the demand that all chemical weapons should be removed and he could even assist the process and participate in the destruction. It would not be part of the mandate of the UN inspectors to identify which country had supplied the weapons or who had stolen them and from whom.
Some will say that to go along with such a proposal would be an unacceptable climbdown for the US. But even President George W Bush offered Saddam what he thought was an exit. He promised days before the deadline in 2003 he would not start the attack if the WMD he believed were present were offered up for destruction. President Bush Sr. also made a somewhat similar offer if Saddam withdrew from Kuwait.
If the proposition to withdraw all chemical weapons were agreed, it would almost certainly be sufficient to bring about an accompanying ceasefire. It would also be an impetus to start the planned conference in Geneva to negotiate a peace settlement.
Such an obvious and simple proposition may, in the frenzied debate that surrounds Syria, appear absurd: we may be told it is a non-starter. But history tells us that it is only at the brink that one has the opportunity to rethink.
The G20 countries are not without a voice or influence when faced by vetoes in the Security Council. If the Permanent Five will not rethink their current stance, then the full General Assembly can use other powers in the UN Charter.
The nearest historical analogy is 1956 when President Eisenhower, with the battle just starting around the Suez Canal between Egypt and the invading forces of France, Israel and Britain, put the weight of the US behind an emergency session of the General Assembly. It was passed by more than a two- thirds majority against the two veto powers, France and the United Kingdom. The fighting ceased and they withdrew their forces.
Circumstances, people will say, are very different today. I am not convinced. True, the US has become very averse to using the Uniting for Peace procedure in the General Assembly during the intervening years. But the fact that this power could be invoked might be an additional spur to the US reassessing its policy towards Syria.
The House of Commons, wisely in my view, slowed the drumbeat to a wider war in the Middle East last week. Far from being ashamed, I am proud of our democratic process in doing so. President Obama has wisely slowed the process even more by deciding to involve Congress in making these decisions. Congress returns to Washington only on 9 September, while the St Petersburg meeting runs from 5-6 September.
The US Congressional debate has started afresh. Senators John McCain and Lindsey Graham have already said they will use their vote to press not for Obama's stated policy of "a shot across the bows" and for action "limited in duration and scope" but for regime change and the overthrow of Assad.
Other concerns are surfacing. What if rockets are fired not from Syria but from Lebanon into Israel and war starts again there? During the first Iraq war in 1991, despite rockets being fired by Iraq into Israel, Bush Sr managed to persuade Israel not to respond. Will the same restraint be available again? I rather doubt it, for Israel sees Iran as being involved in both Lebanon and in Syria. Israel still wants Obama to attack Iranian facilities that it believes are making nuclear weapons. The Middle East is a powder keg. The Sunni/Shiite confrontation is spreading and it is reigniting in Iraq.
Again, history tells us that limited war and micromanagement are very hard to achieve. What starts small ends up large. The huge risks of triggering a wider war by the US intervening in the civil war in Syria, even in the limited way that Obama envisages, lay in my view behind many MPs' rejection of Cameron's and Blair's flawed arguments. Also, they took on board the caution of UK military leaders. After all, the very recently retired Chief of Defence Staff in the UK has made it quite clear he was and still is opposed to action of the sort planned in Syria.
At St Petersburg the rest of the world has an opportunity to intervene for a negotiated peace in Syria. Let us hope they take it.
© David Owen/Global Viewpoint Network