US's Bolton says more sanctions likely on Iran

US National Security Advisor John Bolton said Thursday that more sanctions were possible on Iran just days after a new round of measures touted as the most punishing ever on Tehran entered into force.

Bolton said two rounds of unilateral US sanctions introduced by President Donald Trump in August and most recently on Monday had had a "quite significant" effect on the Iranian economy and the country's actions abroad.

"I think that you're going to see even more sanctions coming into play over time and much tighter enforcement of the sanctions," Bolton told reporters in Paris.

Asked what would be the target of the sanctions, he replied, "There are other things we can do in the terrorism and counterterrorism area." The International Monetary Fund forecasts that the sanctions will cause Iran's economy to contract 1.5 per cent this year and 3.6 per cent next year - pain that Trump has boasted about.

"We've seen indications that it has affected their belligerent activity in Iraq, Syria and Yemen. Not enough yet, but it's beginning to have that effect," Bolton said.

"We've seen a continuation and exacerbation of political discontent inside Iran. That opposition continues to manifest itself. Economically the Iranian currency is going through the floor, inflation has quadrupled and the country is clearly in recession."