U.S. President Barack Obama on Wednesday convened a new round of ambitious Middle East peace talks and told Israeli and Palestinian leaders they have a narrow window of opportunity to settle sharp differences and break decades of hostility. “This moment of opportunity may not soon come again,” Obama said at the White House before hosting Palestinian Authority President Mahmoud Abbas and Israeli Prime Minister Binyamin Netanyahu for their first face-to-face peace discussions in almost two years. “They cannot afford to let it slip away.” Obama sought to lower expectations, noting that it had taken his administration more than one year to get the two sides back to the negotiating table. “The hard work is only beginning,” said Obama, who was flanked by Secretary of State Hillary Clinton and special Middle East peace envoy George Mitchell. “Neither success nor failure is inevitable. But this much we know: if we do not make the attempt, then failure is guaranteed. If both sides do not commit to these talks in earnest, then longstanding conflict will only continue to fester and consume another generation, and this we simply cannot allow.” The U.S. president also noted that many observers and participants in the Arab-Israeli conflict are skeptical or opposed to peace. “We are under no illusions,” he said. “Passions run deep. Years of mistrust will not disappear overnight.” In a carefully arranged series of meetings designed to establish the final groundwork for negotiations, Obama met separately Wednesday with Abbas and Netanyahu as well as with Jordan's King Abdullah II and Egyptian President Hosni Mubarak. They all were scheduled to gather for dinner Wednesday night before Thursday's scheduled beginning of formal negotiations at the State Department.