US President Barack Obama on Wednesday pleaded with Israelis and Palestinians not to let slip a fleeting opportunity for peace, as he opened landmark Middle East talks. 'This moment of opportunity may not soon come again,' Obama warned after holding separate meetings with Israeli Prime Minister Benjamin Netanyahu and Palestinian president Mahmud Abbas and the leaders of Egypt and Jordan. 'They cannot afford to let it slip away. Now is the time for leaders of courage and vision to deliver the peace that their people deserve.' 