PARIS, Dec. 4  The International Atomic Energy Agency on Tuesday publicly embraced the new American intelligence assessment stating that Iran had halted its nuclear weapons effort, but in truth the agency is taking a more cautious approach in drawing conclusions about Iran’s nuclear program.

“To be frank, we are more skeptical,” a senior official close to the agency said. “We don’t buy the American analysis 100 percent. We are not that generous with Iran.”

The official called the American assertion that Iran had “halted” its weapons program in 2003 “somewhat surprising.”

That the nuclear watchdog agency based in Vienna is sounding a somewhat tougher line than the Bush administration is surprising, given that the administration has long criticized it for not pressuring Iran hard enough to curb its nuclear program.