Obama tells Turkish students change will take time

President Barack Obama heralded a "new chapter of American engagement" with the world on Tuesday and vowed to forge new relationships in the Middle East and elsewhere. But he cautioned that turning U.S. policy in a new direction would take time.

"States are like big tankers, they're not like speedboats. You can't just whip them around and go in another direction," Obama said in a question-and-answer session with Turkish college students.

"You turn them slowly, and eventually you end up in a very different place," he said, responding to a student who asked about differences between him and his predecessor.

Obama ended his first overseas trip as president with an appeal to the world to put aside stereotypes and misconceptions: the view by many Muslims that Israel is to blame for all problems, similar views in reverse by "some of my Jewish friends," the view in parts of the world that Americans are crass and selfish.

"The world will be what you make of it," Obama told the students. "You can choose to make new bridges instead of new walls."

Obama ended his eight-day swing with a two-day visit to Turkey, a key NATO ally and the only major member of the alliance that is predominantly Muslim. Obama followed with an unnanounced stop in Iraq before the return flight to Washington.

"You will find a partner and a friend in the United States of America," he told the young people as he sought to repair heavy damage to the U.S.-Turkish relationship caused by the war in Iraq, which Turkey opposed.

Previously, Obama attended the Group of 20 economic summit in London, a 60th celebration of NATO in France and Germany, and a U.S-European Union summit in Prague. On the sidelines, he met for the first time with many world leaders, including the leaders of China, Russia and India.

The White House was quick in issuing its own scorecard on the whirlwind tour.

"America is back," declared Obama's chief of staff, Rahm Emanuel. Senior adviser David Axelrod called the mission "enormously productive."

"You plant, you cultivate, you harvest," Axelrod told reporters. "Over time, the seeds that were planted here are going to be very, very valuable."

Obama's final day in Turkey also featured a meeting with religious leaders and stops at top tourist sites in Istanbul and on the Bosporus, the waterway that connects the Mediterranean and Black seas and serves as the dividing line between Europe and Asia.

Accompanied by Prime Minister Recep Tayyip Erdogan, Obama toured the Hagia Sophia museum and the Blue Mosque.

In the session with students, Obama repeated his pledge to rebuild relations between the United States and the Muslim world.

"I am personally committed to a new chapter in American engagement," Obama said. "We can't afford to talk past one another and focus only on our differences, or to let the walls of mistrust go up around us."

Obama said that despite its flaws and past mistakes, the United States is poised for a fresh start with Muslims and the rest of the world.