The Bush administration is increasingly concerned that Iran's conservatives, who now have an official monopoly on all branches of government, intend to steer Iran on a more radical course on three top issues for the United States and its allies - support for Islamic extremist groups, intervention in Iraq, and the international talks aimed at ensuring Iran does not develop nuclear weapons, said U.S. officials.

A report issued Wednesday by an international watchdog group warned that the consolidation by hard-liners, represented by Ahmadinejad's ascent to the presidency, marks a new challenge for the rest of the world. ''Based on his rhetoric, past performance and the company he keeps, Amadi-Nejad appears a throwback to the revolution's early days: more ideological, less pragmatic and anti-American,'' said the Brussels-based International Crisis Group, an independent, non-governmental organization that works to prevent and resolve global conflict.

Ahmadinejad is likely to ''aggravate tensions'' with Washington, since he is ''dismissive'' of a need to improve relations with Washington, the report said. ''On the foreign front, the style is likely be more confrontational and less appealing to Western audiences.''

After his dark-horse victory in June over better-known politicians, including an ex-president, Ahmadinejad said ''relations with the United States are not a cure for our ills.''

Over the next four years, oil-rich Iran is instead likely to deepen new economic and security partnerships with China, India and South Korea, which have growing energy needs, at the expense of long-standing European ties, ICG predicted. As Tehran's mayor since 2003, Ahmadinejad has visited Beijing, Shanghai and Tokyo, but no European capitals.

Ahmadinejad alone is not the only reason to expect a tougher line from Iran, especially since his administration is expected to focus heavily at first on the domestic economic issues that were largely responsible for his surprise election, said Iranian and U.S. analysts.

''The election has solidified the conservative establishment and given them a deeper self-confidence and sense of legitimacy,'' said Hadi Semati, a Tehran University political scientist now at the Carnegie Endowment for International Peace. ''The energy of self-confidence is likely to make them risk-prone rather than risk-averse. They believe they now have enough leverage to drive tougher bargains on many issues, particularly in nuclear talks.''