President Obama that Palestinian "efforts to delegitimize Israel will end in failure," adding that "symbolic actions to isolate Israel at the United Nations in September won't create an independent state."
In terms of formal U.N. membership, he is correct. Chapter II, Article 4 of the U.N. Charter says, "The admission of any such state to membership in the United Nations will be effected by a decision of the General Assembly upon the recommendation of the Security Council."
That suggests that the U.S., a member of the Security Council, would veto any Palestinian membership if negotiations with Israel do not succeed.
But a U.S. veto may ultimately not matter. An effort is underway at the U.N. to garner support for a General Assembly vote in favor of Palestinian membership. Supporters would have to find a two-thirds' majority of the 193 votes in the General Assembly to prevail.
The plan is to then invoke General Assembly Resolution 377 A (V), which was given the title "Uniting for Peace." Passed in 1950, according to the U.N. treaty documents, it "states that where the Security Council, because of lack of unanimity of the permanent members, fails to exercise its primary responsibility for the maintenance of international peace and security, the General Assembly shall seize itself of the matter." That basically means that the U.N. General Assembly would bypass the U.N. Security Council.
Now, the wording is such that it does not have the force of international law. But there is a reason why Israel's Defense Minister Ehud Barak, referring to the U.N. movement to vote for recognition of a Palestinian state with the 1967 borders, said in March, "We stand to face a diplomatic tsunami." Needless to say, Israel is trying to fend off the vote, and the White House and the U.S. Mission to the U.N. have been supportive. But the plan for the vote is still moving forward.