The diplomatic track attempting to block Iran's quest for nuclear weapons is at a critical stage. Washington has agreed to join the Europeans in talks with Teheran, provided that Iran suspends uranium enrichment and reprocessing activities. Washington's new offer seems tailored to pave the way for agreement on a "carrot and stick" Security Council resolution at Friday's talks in Vienna. What is not clear is whether, in exchange for making the concession of changing its position on talks with Iran, the US reached some level of agreement with China and Russia on jointly backing tough Security Council sanctions if the American offer is rejected or if talks fail. The US offer to talk to Teheran is a risky gambit since it could, particularly if talks actually take place, relieve pressure on the regime and demoralize the growing Iranian opposition. Such an offer would only be worth this risk if it succeeded in bringing Russia and China aboard the US approach. Russia, which has opposed any resolution under the binding Chapter 7 of the UN Charter, reportedly may agree to a compromise, whereby only Article 41 of that Chapter is referred to in the proposed Security Council resolution. This article provides for sanctions "not involving the use of armed force" but possibly including "complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication, and the severance of diplomatic relations." Under Article 41, the UN could cut off the flow of refined oil to Iran that provides 40 percent of the country's fuel needs. The regime clearly regards the price of gasoline as important, since it spends about $3 billion to subsidize gas prices, which would rise markedly in the wake of a refined oil cutoff. Financial sanctions could also hit directly at prominent mullahs who, in addition to running a clerical dictatorship, are among the richest men in the country. Disallowing visas for the Iranian soccer team to participate in the World Cup in Germany, meanwhile, would be a devastating below, as would suspension of diplomatic ties and international travel. The international community must keep in mind that the goal is not just to express condemnation, but to force the Iranian regime to capitulate on what has become - despite frequent denials - Teheran's obvious objective: obtaining the capability to build a nuclear arsenal. This goal is more achievable than it may seem, even without resorting to military force, but only if the United States and Europe show unity and determination on a level that arguably has not been seen since World War II. If the US and the E-3 are determined to prevail, they can impose many of the necessary sanctions on their own, and threaten Russia and China with continuing to act outside the UN Security Council if they don't cooperate. This is a significant threat, because Russia and China have a clear interest in keeping the diplomatic process in a framework where they have a high degree of influence. In addition to the requirement that sanctions be tough enough to influence Iranian behavior, it will also be necessary to require a high standard of verifiability before accepting any concession Iran might make. Nothing less than a full and transparent dismantling of Iran's nuclear programs, as happened in the case of Libya, should be required before any sanctions imposed are lifted. Finally, maintaining Secretary of State Condoleezza Rice's emphasis, in her statement yesterday, on both Iran's nuclear ambitions and its support for terrorism - including Hizbullah - is critical. Again, like in Libya, the nuclear and terror issues must remain linked, with the international community demanding a full end to both.