The US State Department said on Thursday that Iran should first return to the negotiating table with the EU-3 in order to have a resolution of the nuclear issue.

"I think that first what the Iranians have to do is get back to negotiations with the EU-3, something that we have been encouraging all along for them to do ...That has been the focus of what we've been trying to do at the IAEA," State Department spokesman Sean McCormack said at a briefing.

The EU-3, or France, Germany and Britain, have expressed willingness to talk to the Iranians, McCormack said.

The United States has threatened to refer Iran to the United Nations Security Council for possible sanctions.

Meanwhile, Iran has threatened to quit the nuclear Nonproliferation Treaty (NPT) and resume enrichment if it is referred to the UN Security Council.

Source: Xinhua