The most widely touted outcome of last week’s Geneva talks with Iran was the “agreement in principle” to send approximately one nuclear-weapon’s worth of Iran’s low enriched uranium (LEU) to Russia for enrichment to 19.75% and fabrication into fuel rods for Tehran’s research reactor. President Barack Obama says the deal represents progress, a significant confidence-building measure.

In fact, the agreement constitutes another in the long string of Iranian negotiating victories over the West. Any momentum toward stricter sanctions has been dissipated, and Iran’s fraudulent, repressive regime again hobnobs with the U.N. Security Council’s permanent members. Consider the following problems:

• Is there a deal or isn’t there? Diplomacy’s three slipperiest words are “agreement in principle.” Iran’s Ambassador to Britain exclaimed after the talks in Geneva, “No, no!” when asked if his country had agreed to ship LEU to Russia; it had “not been discussed yet.” An unnamed Iranian official said that the Geneva deal “is just based on principles. We have not agreed on any amount or any numbers.” Bargaining over the deal’s specifics could stretch out indefinitely.

Other issues include whether Iran will have “observers” at Russian enrichment facilities. If so, what new technologies might those observers glean? And, since Tehran’s reactor is purportedly for medical purposes, will Mr. Obama deny what Iran pretends to need to refuel it in 2010?

• The “agreement” undercuts Security Council resolutions forbidding Iranian uranium enrichment. No U.S. president has been more enamored of international law and the Security Council than Mr. Obama. Yet here he is undermining the foundation of the multilateral campaign against Tehran’s nuclear weapons program. In Resolution 1696, adopted July 31, 2006, the Security Council required Iran to “suspend all enrichment-related and reprocessing activities, including research and development.” Uranium enriched thereafter—the overwhelming bulk of Iran’s admitted LEU—thus violates 1696 and later sanctions resolutions. Moreover, considering Iran’s utter lack of credibility, we have no idea whether its declared LEU constitutes anything near its entire stockpile.

By endorsing Iran’s use of its illegitimately enriched uranium, Mr. Obama weakens his argument that Iran must comply with its “international obligations.” Indeed, the Geneva deal undercuts Mr. Obama’s proposal to withhold more sanctions if Iran does not enhance its nuclear program by allowing Iran to argue that continued enrichment for all peaceful purposes should be permissible. Now Iran will oppose new sanctions and argue for repealing existing restrictions. Every other aspiring proliferator is watching how violating Security Council resolutions not only carries no penalty but provides a shortcut to international redemption.

• Raising Iran’s LEU to higher enrichment levels is a step backwards. Two-thirds of the work to get 90% enriched uranium, the most efficient weapons grade, is accomplished when U235 isotope levels in natural uranium are enriched to Iran’s current level of approximately 3%-5%. Further enrichment of Iran’s LEU to 19.75% is a significant step in the wrong direction. This is barely under the 20% definition of weapons-grade, highly enriched uranium (HEU). Ironically, Resolution 1887, adopted while Mr. Obama presided over the Security Council last week, calls for converting HEU-based reactors like Iran’s to LEU fuel precisely to lower such proliferation risks. We should be converting the Tehran reactor, not refueling it at 19.75% enrichment.

After Geneva, the administration misleadingly stated that once fashioned into fuel rods, the uranium involved could not be enriched further. This is flatly untrue. The 19.75% enriched uranium could be reconverted into uranium hexafluoride gas and quickly enriched to 90%. Iran could also “burn” its uranium fuel (including the Russian LEU available for the Bushehr reactor) and then chemically extract plutonium from the spent fuel to produce nuclear weapons.

The more sophisticated Iran’s nuclear skills become, the more paths it has to manufacture nuclear weapons. The research-reactor bait-and-switch demonstrates convincingly why it cannot be trusted with fissile material under any peaceful guise. Proceeding otherwise would be winking at two decades of Iranian deception, which, unfortunately, Mr. Obama seems perfectly prepared to do.

The president also said last week that international access to the Qom nuclear site must occur within two weeks, but an administration spokesman retreated the next day, saying there was no “hard and fast deadline,” and “we don’t have like a drop-dead date.” Of course, neither does Iran. Once again, Washington has entered the morass of negotiations with Tehran, giving Iran precious time to refine and expand its nuclear program. We are now even further from eliminating Iran’s threat than before Geneva.