Iranian Foreign Minister Mohammad Javad Zarif has appeared to rule out any new extension to negotiations with world powers over his country's nuclear programme after meeting US Secretary of State John Kerry for new talks.

Kerry and Zarif held a second round of talks in the German city of Munich on Sunday, meeting for about 90 minutes as they try to hammer out a political accord to rein in Iran's nuclear programme ahead of a March 31 deadline. 

Following the talks, Zarif told the conference that progress had been made in the past months and that there was now a window of opportunity to come up with a final deal.

"This is the opportunity to do it, and we need to seize this opportunity," he said. "It may not be repeated."

"I do not think another extension is in the interest of anyone, as I do not believe this extension was either necessary or useful.

"In my view extension is not useful, not conducive to an agreement, and all my energy and focus and that of my colleagues and I'm sure my negotiating partners ... are all focused on reaching an agreement as early as possible."

Iran and six world powers - US, Britain, China, France and Russia as well as Germany - have previously held several rounds of talks intended to scale back Tehran's nuclear programme in exchange for the lifting of sanctions but sticking points remain.

Supreme Leader weighs in

Zarif's comments came as Iranian Supreme Leader Ayatollah Ali Khamenei said on Sunday he would go along with a nuclear deal with the six major powers as long as it was in the best interests of his nation, the Reuters news agency reported.

"I would go along with the agreement in the making," Khamenei said in a speech to air force personnel, as quoted by the official news agency IRNA.

"Our [nuclear] negotiators are trying to take the weapon of sanctions away from the enemy. If they can, so much the better. If they fail, everyone should know there are many ways at our disposal to dull this weapon," he said.

Washington and its partners are hoping to clinch a deal setting long-term limits on Tehran's enrichment of uranium and other activity that could produce material for use in nuclear weapons.

Iran says its programme is solely for energy production and medical research purposes. It has agreed to some restrictions in exchange for billions of dollars in relief from US economic sanctions.

Zarif said all sanctions against his country should be lifted, saying that if they had been intended to stop its nuclear ambitions they had failed. He said when sanctions had been imposed, Iran had 200 centrifuges, and "now we have 20,000".

"Sanctions are a liability, you need to get rid of them if you want a solution," he said. "I think we have made good headway in resolving even that."