Iran warned on Tuesday that Western sanctions against the country's oil exports must be lifted and that their right to a civilian nuclear program recognized, or else Tehran could break off negotiations.

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Iran's delegation said a negative response from EU foreign policy chief Catherine Ashton, who is leading six-power group talking with Iran, would mean "the end of the negotiations in its current configuration.

The ultimatum came as the second day of talks on Iran's disputed nuclear program got under way in Moscow, after little progress was achieved on Monday.

Ashton has said the EU will not budge on an oil embargo set to go into effect July 1 unless Tehran agrees to limit its uranium enrichment to 20 percent.

Even as Iran was threatening to end talks, plans for another meeting in China in a few weeks time were under discussion.