President Obama urged Israeli and Palestinian leaders Wednesday to take advantage of this moment and make peace after decades of conflict, pledging his administration’s sustained support to help them do so.

Appearing in the Rose Garden, Obama spoke sternly to both parties and to the Middle East’s Arab leaders, whom he tacitly scolded for endorsing the creation of a Palestinian state in principle while often doing little to help bring one about.

But he warned that, ultimately, only Israeli Prime Minister Benjamin Netanyahu and Palestinian leader Mahmoud Abbas, with whom he met individually earlier in the day, could make the compromises necessary to secure peace between their peoples.

“The hard work is only beginning,” Obama said. “Neither success nor failure is inevitable. But this much we know – if we do not make the attempt, then failure is guaranteed.”

Obama spoke at the end of a day of meetings with the four leaders who will be involved, either directly or as mediators, in negotiations planned to conclude in one year with the conflict’s most difficult issues resolved.

Those include the status of Jerusalem, which both Israelis and Palestinians claim as their capital; the right of Palestinian refugees to return to homes inside what is now Israel; and the final borders of a Palestinian state.

But a deeply divided Palestinian national movement, a right-leaning Israeli public, and energetic extremes on both sides who oppose compromise of any kind are already complicating efforts to forge a peace agreement, which has eluded Israelis, Palestinians and their U.S. mediators for years.

Obama sought to strike a note of hope in his remarks, tempering it with a realistic assessment of the challenges ahead as Israelis and Palestinians prepare to officially renew direct negotiations today after a 20-month hiatus.

“We are under no illusions,” Obama said. “Passions run deep. Each side has legitimate and enduring interests. Years of mistrust will not disappear overnight.”

Obama met Wednesday with Netanyahu, Abbas, King Abdullah II of Jordan and Egyptian President Hosni Mubarak in one-on-one sessions in the Oval Office, followed in some cases by discussions with a larger group of senior U.S. officials and national delegations.