WASHINGTON - Former Secretary of State Hillary Clinton is siding with President Obama on the issue of sanctions against Iran, saying Congress should hold off on imposing any additional sanctions while diplomatic negotiations run their course.

Clinton conveyed her stance in a letter to Sen. Carl Levin, chairman of the Senate Armed Services Committee, last month.

"Now that serious negotiations are finally under way, we should do everything we can to test whether they can advance a permanent solution," the letter said. "As President Obama has said, we must give diplomacy a chance to succeed, while keeping all options on the table.

"The U.S. intelligence community has assessed that imposing new unilateral sanctions now 'would undermine the prospects for a successful comprehensive nuclear agreement with Iran.' I share that view," Clinton said. "It could rob us of the diplomatic high ground we worked so hard to reach, break the united international front we constructed, and in the long run, weaken the pressure on Iran by opening the door for other countries to chart a different course.

"I have no doubt that this is the time to give our diplomacy the space to work. If it does not, there will be time to put in place additional sanctions in the future, with greater international support necessary to ensure enforcement, and to explore every other option on the table," she said in the letter.

The letter came in response to a request from Levin, who asked her to weigh in on the issue.

"This is a thoughtful, persuasive argument from an experienced, respected senior official," Levin said. "It makes clear Secretary Clinton's belief that tough sanctions helped bring Iran to the negotiating table, and that Congress and the administration are poised to act if Iran violates its commitments or fails to negotiate in good faith toward a final agreement.

"Her letter is another strong signal to Congress that we should not take any legislative action at this time that would damage international unity or play into the hands of hard-liners in Iran who oppose negotiations," he said.

Obama has said he would veto any legislation calling for new sanctions against Iran at this time.