By Bruce Stokes, Director of Global Economic Attitudes, Pew Research Center

In the debate over whether the U.S. and one or more of its NATO allies should launch a military strike against the regime of Syrian President Bashar Assad over its alleged use of chemical weapons, much has been made of the need for multilateral sanction for such an effort, either by the U.N. Security Council or NATO.

One rationale for seeking multilateral backing is legality. The U.N. charter preempts the use of military force except in self-defense or with Security Council approval. But there is precedent for a military strike without U.N. authorization. In 1999 the U.S. and its NATO allies bombed Serbia for 78 days in an ultimately successful effort to force the government of Slobodan Milosevic to withdraw from Kosovo. And in 1998, Washington launched missile strikes against al-Qaida targets in Sudan and Afghanistan.

A second rationale is to provide multilateral political cover for what would be effectively for the most part a unilateral military action by the U.S. However, public opinion data suggest that such cover may be quite thin. Only in Europe is there widespread support for the principle of obtaining U.N. authorization before taking action to deal with international threats. And public faith in NATO among its members is waning.

A 2011 Pew Research Center survey of 23 countries found that in only nine of these nations did a majority or plurality of the public say U.N. approval was needed to deal with international threats. In particular, 50% of the Japanese surveyed thought that U.N. approval should be sought before the use of military force to deal with an international threat and 34% said it was not needed.

In six countries, majorities or pluralities thought seeking approval was unnecessary. Publics were divided in eight other nations. Moreover, in nearly half the countries, one-in-five of those surveyed voiced no opinion on U.N. approval of the use of force.

Notably in the wake of London’s failed Aug. 28 attempt to get Security Council approval for some form of military action in Syria, only in Western Europe – Germany (76%), Spain (74%), Britain (67%) and France (66%) – did strong public majorities back the principle of U.N. authorization. Americans were divided: 45% thought approval was needed, 44% did not.

Roughly half or more of the publics in countries neighboring Syria did not support the principle of seeking U.N. blessing for military action, including 59% in the Palestinian Territories, 54% in Jordan, and about half in Egypt and Lebanon.

In Lebanon, only 10% of Lebanese Shia, who generally back the Assad regime, thought U.N. sanction was necessary. Meanwhile, 59% of Lebanese Sunnis, many of whom support the Syrian rebels who might benefit from a Western military strike, believe U.N. approval is necessary.

Both the Chinese and the Russian governments oppose any U.N. approval of military action against Syria. Ironically, at least in principle, their publics do not think such approval is even needed for military actions. In 2011, only a quarter of Russians thought it was necessary to seek Security Council backing before using military force to deal with international threats, while only 38% of Chinese saw a need to first go to the U.N. to obtain its blessing.

Obama’s dilemma

With the British Parliament’s rejection of U.K. military action, the Obama administration’s effort to cobble together a coalition of willing NATO allies to join the U.S. in any attack now may only include France and possibly Turkey.

This NATO-lite effort comes at a time of waning support for the multilateral security organization, especially in Western Europe. Since 2009, NATO favorability is down 14 percentage points in Spain (to 42%) and Germany, and 13 points in France (to 58%), according to a Pew Research Center survey done before the most recent allegations of chemical weapons use by the Syrian government. Only about half of Americans see NATO in a favorable light, virtually unchanged from 2009.

Although Turkey is a long-time NATO member, Turkish public support for the security alliance is also quite weak. Just a quarter of Turks have a favorable view of NATO today, although that is a 10 percentage point improvement over NATO backing just a year ago.

How a U.S.-led military strike against Syria might affect public views of the alliance is unknown. But an Aug. 26-28 survey in France by the newspaper Le Figaro found that 59% of the public was opposed to military action by France even if it has U.N. approval. An Aug. 28 poll by ZDF television in Germany, meanwhile, showed that 55% of the public opposed any financial or material support of a U.S. strike against Syria. And in a March 2013 Pew Research Center survey, two-thirds of Turks were against Western countries even sending arms and military supplies to the anti-government groups in Syria.

All this suggests that the effort to gain multilateral backing and participation for a military strike on Syria may not actually result in the publicly condoned political cover that the administration seems to be hoping for.