President Bush on Tuesday pledged to work with the United Nations' new leader for peace across war-torn and troubled areas of the world.

Bush met in the Oval Office with Ban Ki-moon, the new U.N. secretary-general.

Talking with reporters later, Ban called the situation in the Middle East a "source of grave concern."

"Iraq and elsewhere needs an urgent attention of the international community," Ban said. "Particularly when it comes to Iraq, the international community should have all possible assistance to help Iraqi government and people to restore peace and stability and recover from economic devastation."

Posing for pictures with Ban, Bush said that, "The United States wants to work with the United Nations to achieve a peace through the spread of freedom."

Ban said he was humbled by the challenges he faces and that he will need the support of the United States in areas such as Lebanon, North Korea and Somalia.

"All are global issues which require global wisdom and effort."

The Bush administration has complained that the U.N. bureaucracy is bloated and needs to adopt reforms to streamline its procedures. Ban said he was reviewing possible reforms.

"The United Nations should change with much more efficiency and effectiveness and mobility, and highest level of ethical standard," Ban said. "I'm very much committed to carrying out this reform and I need strong support of all member states and staff of the United Nations in carrying these reform measures."

The meeting came at a time of transition at the U.N. for the United States. Bush has announced he will nominate the U.S. ambassador to Iraq, Zalmay Khalilzad, to be the next U.S. envoy to the United Nations. Khalilzad, who is Afghan born, has also served as ambassador to Afghanistan. He will replace John Bolton, who could not win Senate confirmation and resigned last month as his temporary appointment as U.N. ambassador was about to expire.