The assembly of more than 170 world leaders to mark the United Nations' 60th birthday gives Secretary of State Condoleezza Rice (search) a unique opportunity to advance U.S. foreign policy goals on several difficult fronts.

Success is by no means assured. While the United States is the largest contributor and the world's only real superpower, it cannot count on the United Nations (search) for automatic support.

Rice's lobbying, and President Bush's appearance before the world body Wednesday, come at a moment when the United States is looking unusually vulnerable to foreign eyes following Hurricane Katrina's (search) devastation and international opposition to the war it is leading in Iraq.

Rice's drive to pressure Iran to resume negotiations on its nuclear program is a key test. Any U.S. resolution in the U.N. Security Council to censure Iran or to impose sanctions runs the risk of being vetoed.

So Rice is appealing openly to China and Russia, which have veto power, to join in sending a "unified message" to Tehran.

Russia remains dubious about having the council take up the issue. On Friday, Deputy Foreign Minister Alexander Yakovenko called it a hasty step.

Rice is using the convergence of world leaders to try to advance two Mideast goals: pressure on of Syria to keep hands off Lebanon and to spur Israel and the Palestinians to use the momentum Israel's withdrawal from Gaza to move toward creation of a Palestinian state.

She plans to meet with Arab and European leaders on Syria as a U.N. inquiry explores whether Syria played a role in the assassination of former Lebanese Prime Minister Rafil Hariri last February in Beirut.

Syrian President Bashar Assad has canceled plans to attend U.N. sessions.

On Mideast peacemaking, the goal of a Palestinian state already has the support of most U.N. members. Rice will meet with U.N., European and Russian officials who joined the United States in devising a blueprint or roadmap for negotiations between Israel and the Palestinians.

On another front, U.N. reform, U.S. Ambassador John R. Bolton (search) and Rice are seeking management changes and new approaches on terrorism and human rights. The outlook is uncertain.

Rice has a heavy schedule this week, meeting with dozens of foreign ministers. She also is budgeting considerable time for a round of media interviews.