Washington, Dec 13 (IANS): Brian Hook, the US Special Representative for Iran, has defended the American sanctions policy on Tehran when experts raised doubts about its effectiveness.

"The sanctions we have imposed on the (Iranian) regime are the toughest ever, they are making an enormous difference," he said at a public event on Thursday in Washington.

The sanctions are "meaningfully" targeting the revenue streams the Iranian government relies on, he noted.

Following its unilateral exit last year from the 2015 Iran nuclear deal, Washington has been mounting pressure on Tehran through a series of sanctions to seek re-negotiations, reports Xinhua news agency.

Iran has maintained a tough stance and scaled back its nuclear commitments in response.

Meanwhile, experts have doubted the effectiveness of the US economic sanctions in terms of seeking a new deal or easing tensions in the Middle East.

"Maintaining a policy of trying to bring down the Iranian regime by destroying its economy carries enormous costs and risks, for the Iranian people but also for the US and its partners throughout the region," wrote Philip Gordon and Robert Malley, American foreign policy experts, in an article published at the Foreign Policy website.

"Further steps to asphyxiate Iran's economy will backfire even in terms of the White House's stated goals: to moderate Iran's regional behaviour and compel it to agree to more stringent nuclear restraints," they added.