By Michelle Moghtader and Fredrik Dahl
DUBAI/VIENNA (Reuters) - Iran has confirmed it tested a new centrifuge that could speed up its enrichment of uranium but rejected a U.S. think-tank's suggestion the move may have violated last year's nuclear deal with world powers.
Foreign Ministry spokeswoman Marzieh Afkham gave no indication that Iran had stopped feeding natural uranium gas into the so-called IR-5 centrifuge. Washington said on Monday Tehran had ceased the activity.
Asked about the U.S. statement, Iran's ambassador to the International Atomic Energy Agency (IAEA), Reza Najafi, said there had been intermittent testing of the IR-5.
"So sometimes you feed, sometimes you do not feed," he told Reuters in Vienna. "If they want ... they can consider that it is stopped. But it is ordinary R&D (research and development) and we are doing that. We continue with R&D."
The comments underlined difficulties of interpretation facing powers seeking a deal with Iran by a Nov. 24 deadline on Tehran's nuclear program which the West fears aims at developing nuclear weapons. Iran denies such ambitions.
Iran's development of advanced centrifuges is sensitive because, if successful, it could enable it to produce potential nuclear bomb material at a rate several times that of the decades-old model now in use. Iran says it is only producing enriched uranium to fuel nuclear power plants.
The IR-5 is one of several new models that Iran has been seeking to develop to replace its erratic IR-1 centrifuge.
Last year's interim nuclear agreement between Iran and the six global powers said Tehran could continue its "current enrichment R&D practices", language that implies it should not expand them.
Unlike other advanced models under development -- IR-2m, IR-4 and IR-6 -- at a research site at its Natanz enrichment plant, Iran had until now not fed the IR-5 with uranium gas.
After an IAEA report on Friday said Iran had been feeding the IR-5 with uranium gas, the U.S.-based Institute for Science and International Security (ISIS) said this may have been a violation of the accord.
Afkham dismissed the allegation as "psychological warfare".
Other U.S. experts said they no saw no breach of the agreement between Iran and the United States, France, Germany, China, Russia and Britain - designed to buy time for talks on a permanent settlement by the Nov. 24 deadline.
(Writing by Parisa Hafezi and Fredrik Dahl; editing by Ralph Boulton)