Taking off his shoes as tradition requires, Obama stepped into the 16th-century Sultanahmet Mosque in the ancient heart of Istanbul, accompanied by Turkish Prime Minister Recep Tayyip Erdogan amid tight security in the area.

Two Muslim preachers guided Obama inside the grandiose edifice - better known as the Blue Mosque for its blue tileworks - and the president smiled when they showed him a dome scripture mentioning the Prophet Mohammed's grandson Hussein, Obama's middle name, Anatolia news agency reported.

In a major speech at the Turkish parliament in Ankara Monday, Obama declared that the United States "is not and never will be at war with Islam" and called Turkey a "critical ally," earning himself much praise in a country where his precedessor left the U.S. image in tatters.

"Obama conquers hearts," the popular Vatan newspaper trumpeted on its front page, while the liberal Taraf said the speech marked the end of "the bellicose spirit of Sept. 11."

Following up on his appeal for dialogue and inter-faith understanding, Obama met yesterday with Muslim, Christian and Jewish spiritual leaders based in Istanbul, Turkey's largest city and the meeting point of Europe and Asia. He combined his visit to the Blue Mosque with a tour of the 6th-century Hagia Sophia church, a masterpiece of Byzantine architecture across the Islamic edifice. Obama also met with university students before wrapping up his two-day visit to Turkey and his debut trip to Europe later yesterday.

A Turkish security official said yesterday a man was detained in Istanbul last week on suspicion he plotted to kill Obama. But police then established the man was mentally disturbed and released him.

Since his election, Obama has already won significant popularity in Turkey, a NATO member and a key Muslim ally of the United States, and is keen to improve ties that chilled over the U.S. invasion of neighboring Iraq in 2003 and former president George W. Bush's policies in the Middle East.

A public opinion poll found in February that 39.2 percent of Turks had confidence in Obama, making him "the most trusted leader" in Turkish eyes. In 2005, only 9.3 percent said they trusted Bush, giving him only a slight lead over al-Qaeda leader Osama bin Laden, who had the confidence of 4.6 percent.

On Monday, Obama hardened his message in support of Turkey's bid to join the European Union, despite French and German opposition.

Turkey and the United States, he said, could set an example to the world by building a "model partnership" based on democratic values. In more pointed messages, Obama called on Turkey to step up EU-demanded democracy reforms and broaden the freedoms of non-Muslim minorities and the restive Kurdish community.

He urged normalization of ties with Armenia, while signaling that Washington would not interfere in their dispute on whether the mass killings of Armenians under the Ottoman Empire in the early 20th century was genocide.

Obama's decision to include Turkey in his first trip to Europe is largely seen as an effort to keep the country firmly anchored in the West.