ISTANBUL, Turkey -- President Bush criticized unnamed U.S. allies in the Middle East for compromising with extremists and suppressing dissent and called on the Islamic world to move toward democracy as a way to safeguard the United States and reduce violence in the Middle East.

Speaking in front of a waterfront mosque, Bush said leaders throughout the Middle East, "including some friends of the United States, must recognize the direction of the events of the day. Any nation that compromises with violent extremists only emboldens them and invites future violence," he said.

"Suppressing dissent only increases radicalism. The long-term stability of any government depends on being open to change and responsive to citizens," Bush said.

The president did not specify which U.S. allies he was referring to, but an aide and outside experts said Saudi Arabia was among them. Some U.S. officials have accused the kingdom's government of lack of energy in suppressing al-Qaida terror network cells within its borders.

Bush went on to praise Turkey, a predominantly Muslim nation that became a secular state in 1924, as "a great and stable democracy, and America shares your hope that other nations will take this path."

Bush called a democratic transformation of the Middle East "one of the great and difficult tasks of history."

"Nations in the region will have greater stability because governments will have greater legitimacy," he said. "And nations like Turkey and America will be safer because a hopeful Middle East will no longer produce ideologies and movements that seek to kill our citizens."

Bush offered no specific new proposals in his speech or details about how he planned to carry out previously announced visions to promote Middle East democracy. He spoke after leaving the closing session of a two-day summit of the NATO alliance.

Bush's visit to Turkey was tense from beginning to end, with massive protests and security precautions wherever he went. One major breach of security was reported: a small bomb exploded yesterday aboard a Turkish Airlines passenger jet parked at the Istanbul airport from which Bush departed several hours later. The device was concealed in a leather wallet left on the cabin floor near the door of the aircraft. The explosion injured three aircraft cleaners. There was no claim of responsibility.

A major theme of Bush's speech was to encourage Iraq, a predominantly Muslim country where an interim government assumed power Monday, to develop a secular democracy that includes protections for minority religious groups. He called for similar changes in Iran and Syria.

Bush singled out Iran as a theater for the "struggle between political extremism and civilized values," saying, "Tired, discredited autocrats are trying to hold back the democratic will of a rising generation."

Bush spoke yesterday against the backdrop of the Bosporus Bridge, which spans the Bosporus Strait that divides the European and Asian shores of Istanbul.

The White House tried to play up the historical flavor of the setting by renting Ottoman-style chairs with gold-painted backs and bright red cushions.