WASHINGTON — With the Obama administration in its final year, several officials have said that the president has grown so frustrated with trying to revive Middle East peace talks that he may lay down his own outline for an Israeli-Palestinian two-state peace agreement, in the form of a resolution in the United Nations Security Council.

If that happens, count on two reactions: Israel’s prime minister, Benjamin Netanyahu, will oppose it, and a chorus of American politicians and commentators will suggest that it would be unprecedented — even unthinkable — for an American president to support a Security Council resolution that Israel opposed, rather than veto it.

Last spring, when similar reports circulated, Senator John McCain of Arizona said that such an action would “contradict American policy for the last at least 10 presidents of the United States.” The Republican chairman and ranking Democrat of the House Foreign Affairs Committee joined in a letter protesting that “for decades the U.S. has used its U.N. Security Council veto to protect Israel from undue pressure at the world body.” A bipartisan group of senators agreed, seeking assurances that the policy would not change.

Remarkably, the assumption beneath those protests — that President Obama would be committing an unprecedented betrayal of the American-Israeli relationship if he did not block every Security Council resolution that challenged the actions or positions of Israel’s government — has gone unchallenged.