National security adviser Thomas Donilon, at Brookings, said Tuesday that the Obama administration’s policy on Iran has been unequivocal. (Alex Wong/GETTY IMAGES)

Three weeks after the release of a U.N. report that documented evidence that Iran is secretly working toward a nuclear bomb, national security adviser Thomas Donilon said that, although Iran continues to engage in “dangerous and destabilizing” behavior, the administration’s policy had raised the cost of Iran’s intransigence.

“Iran today is fundamentally weaker, more isolated, more vulnerable and badly discredited than ever,” Donlion said at the Brookings Institution. “Compared to when President Obama took office, Iran is greatly diminished — at home, in the region, and around the world.”

Along with international allies, the Obama administration has imposed wide-ranging sanctions on Iran, while holding out the possibility of engagement with the country’s leadership. On Monday, the administration sought to further squeeze the country, designating its entire financial sector a “money laundering concern,” a move intended to discourage companies from doing business with Iranian banks. Britain and Canada also imposed more sanctions.

Republican lawmakers have pushed the administration to go even further — including freezing the assets of the Central Bank of Iran, a step that some fear could destabilize the world economy. Meantime, fears that  Iran is edging closer to a nuclear “breakout” have led to heightened anxiety in the region, with concerns that Israel could attempt to launch a preemptive strike.

Donilon said the administration’s policy has “reassured our partners in the region” and helped to “demonstrate unmistakably to Tehran that any attempt to dominate the region will be futile.”

Sanctions, Donilon said, have made it not only more difficult for Iranian banks to access the international financial system, but more difficult for the government to purchase what it needs to develop the oil and natural gas sector.

“If Tehran does not change course, the pressure will continue to grow,” he said. “Working with allies and partners, we will continue to increase sanctions. ... We will continue to build a regional defense architecture that prevents Iran from threatening its neighbors. We will continue to deepen Iran’s isolation, regionally and globally. And, again — even as the door to diplomacy remains open — we will take no option off the table.”

The recent report on Iran from the International Atomic Energy Agency acknowledged uncertainty about whether the country’s weapons research is ongoing. Output from its main uranium-enrichment plant has held steady or fallen in recent months, a phenomenon that could be the result of not only sanctions but technical problems.

Still, the IAEA said it has “serious concerns” that Iran was working toward a nuclear bomb, directly contradicting assertions from President Mahmoud Ahmadinejad and others that the country’s nuclear work was entirely peaceful.