New York  - Acknowledging that reaching a peace deal in the Israeli-Palestinian conflict "will be difficult," US President Barack Obama said Wednesday the world must put aside politics and get "serious" about achieving a settlement.

Obama called on all UN members at the opening of the General Assembly to recognize the legitimacy of Israel's existence while insisting the Jewish state respect the rights of Palestinians.

"The United States does Israel no favours when we fail to couple an unwavering commitment to its security with an insistence that Israel respect the legitimate claims and rights of the Palestinians," Obama said.

Obama has declared reaching a peace settlement among his top foreign policy priorities and has invested a significant amount of effort to do so in his young administration.

"I know this will be difficult. But all of us must decide whether we are serious about peace, or whether we only lend it lip-service," he said.

Obama held meetings with Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas on Tuesday. Under Obama, the United States and Israel have had a rare public disagreement over Obama's demands the Netanyahu halt any new settlement construction or expansion.

"To break the old patterns - to break the cycle of insecurity and despair - all of us must say publicly what we would acknowledge in private," he said.  dpa