Barack Obama is unlikely to have much trouble forming a Nato coalition if Washington decides on military intervention in Syria after the alleged chemical weapons atrocities by the regime of Bashar al-Assad.
But there is no prospect of a UN mandate for international military action over Syria, with the Kremlin - enraged at what it saw as abuse of a UN mandate to topple Muammar Gaddafi in Libya - as well as China certain to keep wielding their veto.
While support is growing in the West for a tough response, Beijing called for a "cautious" approach. "All parties should handle the chemical weapons issue cautiously to avoid interfering in the overall direction of solving the Syria issue through political settlement," Foreign Minister Wang Yi said.
"China has paid high attention to the reports that chemical weapons have been used in Syria," Wang said. "We will firmly oppose anyone who uses chemical weapons."
Turkey, which accounts for Nato's second largest army after the US, and which is on the frontline with Syria, is already a key conduit for arms supplies to, and a safe haven for, groups of fighters at war with Damascus.
It has been the loudest critic of the Assad regime, clamouring for the West to do more. In any international coalition Turkey would likely play a key role.
Britain and France, the EU's only military powers with the capacity and will to project military muscle abroad, look certain to line up with the Americans.
Yesterday, the German government suggested for the first time that it would support an international military response if UN inspectors confirm the use of chemical weapons. "Germany would be among those who consider consequences to be appropriate," Foreign Minister Guido Westerwelle said.
Since the reports of chemical weapons use, Laurent Fabius, the French foreign minister, has been among the loudest arguing "something must be done".
On Sunday, on a visit to Israel, he repeated France's demand for a strong response to the allegations. In meetings last week that echoed the run-up to the Anglo-French-led campaign in Libya, Fabius also discussed options with British Foreign Secretary William Hague.
Israel is also likely to support the Americans, although intensely worried about the form and substance of a post-Assad Syria.
Shimon Peres, the Israeli president, after meeting Fabius, called for an international operation to remove chemical weapons from Syria.
"The time has come for a joint effort to remove all the chemical weapons from Syria. They cannot remain there either in the hands of Assad or of others. I understand the problems and doubts ... but the moral call is superior to any strategic considerations."
France and Britain took the lead in the international effort to unseat Gaddafi, citing the risks of a bloodbath attending the potential fall of rebel-held Benghazi.
The French, with British support, also intervened militarily last year in Mali to pre-empt the rise of Islamist militias.
Since the start of the year, Britain and France have led the campaign to alter EU sanctions against Syria to lift the arms embargo on rebel forces.
This weekend about 400 tonnes of arms went to the rebels across the Turkish border in what was described as one of the biggest weapons shipments ever.
Given the absence of a UN mandate, the 1999 Nato Kosovo intervention would give the most apt precedent for action, on the grounds of humanitarian intervention. Analysts say the US will not want for justification for intervention if the White House decides on using force in Syria.
Additional reporting by Associated Press and Agence France-Presse