It is unfortunate that President Obama, who has been thoughtful and cautious about putting America into the Syrian conflict, has created a political situation in which his credibility could be challenged.

He did that by publicly declaring that the use of chemical weapons would cross a red line that would result in an American response. Regardless, he should have long ago put in place, with our allies and partners, a plan for international action — starting with tough sanctions — if President Bashar Assad used chemical weapons.

It is alarming that Obama did not.

Meanwhile, the United Nations Security Council, which has the responsibility to uphold treaties outlawing chemical weapons use, has failed to act in any way following the August attack, largely because of the opposition of Russia, Assad’s chief ally and arms supplier, and China.

It is appalling that Russia and China have not been the focus of international outrage and pressure.

The Arab League, representing some of the world’s most anti-Assad governments, on Sunday toughened its previous position when it called on the United Nations and the international community to take “necessary measures” against Syria’s government.

But, feckless as ever, the League did not specify what measures it supported and, on Monday, the League’s secretary general said there should be no military action without a green light from the United Nations.