Tehran announced Tuesday that it inserted more than 100 fuel rods into the main core at its Bushehr nuclear reactor. The move comes despite mounting economic pressure on Iran to come clean on its nuclear program.
Washington and many of its Western-backed allies say Iran's nuclear program is cover for more malicious activities. Tehran maintains that it is operating within its rights.
Dennis Ross, a special assistant to U.S. President Barack Obama, told members of the American Israel Public Affairs Committee that Iran's behavior shows it favors belligerence.
"Iran's own behavior," he said in his statements, "has demonstrated that it prefers defiance and secrecy to transparency and peace."
Iranian authorities in response to the Bushehr activity said they've won in the battle over nuclear issues.
Meanwhile, Ross complained that Iran's human rights record and interference in regional affairs relegated Tehran to a counter-productive force in the international community.
"There is no question Iran has been surprised by the magnitude of the sanctions and the depth of support for them in the international community," he said. "They can no longer rely on those in the international community they thought would block such measures on their behalf."