The United States expects Security Council agreement on UN sanctions against Iran within weeks unless Teheran does a last-minute turn and agrees to freeze uranium enrichment, a senior US State Department official said Friday. US Undersecretary of State Nicholas Burns additionally dismissed suggestions of cracks in the six-power coalition pushing Teheran to give up enrichment, in comments a day after those countries ended confidential discussion on Iran in the German capital. Burns said further talks were needed on how harshly to penalize Teheran for its refusal to freeze uranium enrichment, as demanded by the Security Council, but a lot of progress was made at those discussions.