TEHRAN, Iran – Iran removed seals from its nuclear facilities on Tuesday and said it had resumed research work, intensifying its standoff with the United States and European powers over its nuclear ambitions.

Iran announced plans last week to resume research on the production of nuclear fuel, heightening concerns that Tehran was moving toward building atomic weapons. Iran says the research is aimed at generating electricity.

Inspectors from the International Atomic Energy Agency agency affixed the seals more than two years ago after Iran agreed to the measure in an effort to dampen suspicions about its nuclear ambitions.

IAEA inspectors were present on Tuesday as Iranian officials began removing the seals, said Melissa Fleming, a spokeswoman for the U.N. agency. She spoke from Vienna, where the agency is based.

Fleming said the 35 nations on the agency’s board of governors would be informed later in the day about what exactly the Iranians planned to do with the equipment.

She declined to say whether the Iranians planned to start enriching uranium or would stop short of that and be satisfied with testing the equipment used in the process.

But Mohammad Saeedi, the deputy head of Iran’s Atomic Energy Organization, said Iran was not resuming the production of nuclear fuel, a process that would involve uranium enrichment.

“What we resume is merely in the field of research, not more than that,” he said at a news conference. “We make a difference between research on nuclear fuel technology and production of nuclear fuel.

“Production of nuclear fuel remains suspended.”