Iran's nuclear chief is expected to outline Iran's refusal to give up uranium enrichment at a 155-nation meeting of the International Atomic Energy Agency on Monday.

At the meeting, which will focus on Tehran's contentious atomic program, as well as Mideast tensions over Israel's alleged nuclear capabilities, Fereydoun Abbasi is expected to explain that Iran needs to enrich unranium to make reactor fuel. The UN Security Council has ordered Tehran to stop the activity, however, because of fears it might use it to produce nuclear warheads.

Meanwhile, European Union foreign policy chief Catherine Ashton is scheduled to meet with Iran's chief nuclear negotiator Saeed Jalili in Istanbul on Tuesday in follow-up talks to negotiations on Iran's atomic program, a spokeswoman for Ashton said on Monday.

The meeting is "part of continuing efforts to engage with Iran" following talks between world powers and Iran in Moscow in June which failed to secure a breakthrough in the dispute over Tehran's nuclear program

"While it is not a formal negotiating round, the meeting will be an opportunity to stress once again to Iran the need for an urgent and meaningful confidence-building step" and to show more flexibility with proposals put forward by world powers in earlier talks in Baghdad, the spokeswoman said.

Iran denies any interest in nuclear weapons. But it has refused to stop enrichment, despite offers of reactor fuel from abroad. It dismisses IAEA suspicions that it worked secretly on nuclear arms.

Israeli Prime Minister Benjamin Netanyahu warned on Sunday that Iran would be on the brink of nuclear weapons capability in six to seven months, adding new urgency to his demand that President Barack Obama set a clear "red line" for Tehran in what could deepen the worst U.S.-Israeli rift in decades.

Taking his case to the American public, Netanyahu said in U.S. television interviews that by mid-2013, Iran would be 90 percent of the way toward enough enriched uranium for a bomb. He urged the United States to spell out limits that Tehran must not cross or else face military action - something Obama has refused to do.

"You have to place that red line before them now, before it's too late," Netanyahu told NBC's "Meet the Press" program, saying that such a U.S. move could reduce the chances of having to attack Iran's nuclear sites.