Iran has just announced plans to triple its production of uranium enriched to the level used in research reactors. This step may seem merely technical to the average person, but it has vast implications. Once accomplished, this feat will elevate Iran to a "virtual" nuclear weapon state. Enriching to the level planned accomplishes 90 percent of the work needed to reach weapon grade, and will put Iran only a few months away from being able to fuel a handful of nuclear weapons. Iran will have the power to do so at any time, at its choosing.

This step also says a lot about Iran's intentions. Iran has no need for this additional enriched uranium in its civilian nuclear program. It already has enough of it for its claimed purpose of fueling its small research reactor. The only visible use for the additional amount is the ability to fuel bombs. Even more worrisome is Iran's plan to move this sensitive work from its above-ground pilot plant at Natanz to the underground and fortified Fordow plant near Qum.

So, shouldn't something be done? The Obama Administration has greeted this announcement meekly. The administration has been content to point to the existing trade sanctions, and to brag about how they are beginning to hinder Iranian businesses. But the sanctions are not dissuading Iran's leaders from their nuclear quest, and have little hope of doing so before Iran achieves its goals.

It is time to think about new tactics, and they could start with candor. There is little to be gained by the present U.S. mealymouthing about Iran's intentions, in which one U.S. official or another is quoted anonymously as saying that Iran is or is not going for the bomb. The evidence is damning; it is time to say so.

In addition to the new uranium enrichment, the Iranians have been caught doing things that can only be on a bomb maker's checklist. They include using uranium deuteride to produce a short burst of neutrons (the only use for which is to initiate the chain reaction in a fission bomb), producing uranium metal and shaping it into nuclear-sized components (useful only for making the metal core of a fission bomb), using special detonators to produce an implosive spherical shock wave (needed to compress the core before setting off the chain reaction in a fission bomb), and testing high voltage firing equipment to insure that it can fire detonators over long distances (needed for nuclear weapon testing). None of this is needed for civilian nuclear work; all of it is needed for a bomb.

What might President Obama do? He could start by declaring forthrightly that the United States believes Iran is trying to build nuclear weapons. Such a declaration is an indispensable predicate for effective action -- even for enforcing the present sanctions. If we aren't sure what Iran is trying to do, why get excited? But we are sure. We know that Iran wants to be able at the very least to deploy nuclear weapons when it chooses.

After declaring that Iran is going for the bomb, the president could also say forthrightly what he plans to do about it. So far, that information has been absent. The present economic sanctions are a starting point, but they are not connected to any specific act by the Iranians. They contain no red lines. The president could paint some.

He could start with the new plan to boost uranium enrichment. It has not begun, so there is time to head it off. The president could state that this enrichment has no use other than to make bombs, and could demand that any further effort to boost enrichment be stopped. Likewise, the president could state that the discovery of work on additional uranium enrichment plants would be seen as further proof of nuclear weapon intent. Iran has no need for such plants, except as part of a covert bomb program. He would be on firm legal ground -- the enrichment is already banned by U.N. resolutions. International inspectors, who are still visiting Iran, could do the verification. The United States could warn that if enrichment weren't stopped, a policy of further isolating Iran from the world would follow.

The president would have to take some risks. Would the United States be willing to enforce a ban on Iranian imports of refined petroleum products (if rationing hasn't rendered this penalty obsolete) or a ban on energy exports? Would the United States be willing to interdict shipments in order to enforce such embargos? Is the United States prepared to target foreign energy companies that invest in Iran, even if these companies are in countries like China? Would the United States ban all American transactions with Iranian banks and companies, specifically transactions by foreign subsidiaries of American companies? Would the United States even ban American transactions with foreign banks and companies doing large amounts of business with Iran? These are among the difficult options the United States would have to choose from if Iran crossed the red lines. Would the United States be prepared to pressure its allies to join, even if some of these things were acts of war?

The present policy is to avoid confrontation. The benefit is political calm, but the cost is missed opportunities to change Iran's behavior -- and the increased likelihood that Iran will emerge as a virtual nuclear weapon power. As Iran passes one nuclear milestone after another, it is hard to see what might prevent Iran's success. Red lines might or might not work, but at this juncture, they might be worth the risk.