Related: U.S. says it must retain option of preemption

    WASHINGTON, March 16 (Xinhuanet) -- U.S. President George W. Bush claimed on Thursday that Iran could pose the greatest challenge to the United States and reaffirmed his strike-first policy.

    In a 49-page national security strategy report, Bush reiterated the preemptive policy he first outlined in 2002, although diplomacy is still the U.S. preference in halting the spread of nuclear and other heinous weapons, he said.

    "If necessary, however, under long-standing principles of self-defense, we do not rule out the use of force before attacks occur, even if uncertainty remains as to the time and place of the enemy's attack," Bush said.

    "When the consequences of an attack with weapons of mass destruction are potentially so devastating, we cannot afford to stand idly by as grave dangers materialize. ... The place of preemption in our national security strategy remains the same."

    On Iran, Bush said, "We may face no greater challenge from a single country than from Iran. For almost 20 years, the Iranian regime hid many of its key nuclear efforts from the international community, yet the regime continues to claim that it does not seek to develop nuclear weapons."

    "The United States has joined with our European Union partners and Russia to pressure Iran to meet its international obligations and provide objective guarantees that its nuclear program is only for peaceful purposes. This diplomatic effort must succeed if confrontation is to be avoided."

    On the Islamic Resistance Movement (Hamas), Bush said, the burden for achieving peace between the Palestinians and Israelis had shifted to Hamas.

    "The opportunity for peace and statehood -- a consistent goal of this administration -- is open if Hamas will abandon its terrorist roots and change its relationship with Israel."

    The long-overdue document, an articulation of U.S. strategic priorities, lays out a robust view of America's power and an assertive view of its responsibility to bring change around the world, the Washington Post said on Thursday.

    "That strategy shifted U.S. foreign policy away from decades of deterrence and containment toward a more aggressive stance of attacking enemies before they attack the United States," the paper said.

    Bush's reiteration of taking preemptive strikes "could be seen as provocative at a time when the United States and its European allies have brought Iran before the UN Security Council to answer allegations that it is secretly developing nuclear weapons," it added.

    The White House continues to describe an Iran with nuclear armsas a "grave threat to the security of the world," it added.

    However, some American security experts and critics are reluctant to accept Bush's doctrine of preemptive war.

    "Preemption is and always will be a potentially useful tool, but it's not something you want to trot out and throw in everybody's face," said Harlan Ullman, a senior adviser at the Center for Strategic and International Studies.

    "To have a strategy on preemption and make it central is a huge error," he said, noting a military attack against Iran could be "foolish," and it would be better to seek other ways to influence Tehran.

    Security specialists said Bush's report had no legal force of its own but served as a guidepost for agencies and officials drawing up policies in military, diplomatic and other fields.   Enditem