Iran is weathering three sets of U.N. Security Council sanctions meant to punish its refusal to freeze its uranium-enrichment program. Its recent rejection of a plan meant to strip it of most of its enriched stockpile plus its belated acknowledgment that it had been secretly building a new enrichment facility has increased sentiment for a fourth set. The United States, Britain and France support such a measure, with Russia undecided and fellow permanent Security Council member China -- which depends an Iran for much of its energy needs -- opposed.