Or they can settle for a milder rebuke of Tehran that leaves the big powers formally speaking with one voice but leaves the world’s hands tied in investigating the suspicions about the Islamic republic.
Both ways, the United States, Britain, France and Germany stand to lose as they head into the opening session of the International Atomic Energy Agency’s (IAEA) 35-nation board meeting.
That may doom further attempts to speak with one Security Council voice at any future negotiations with Iran over its nuclear defiance - and increase Sino-Russian resistance against new U.N. Security Council sanctions on Tehran.
Going too far the other way keeps the facade of unity, by allowing Moscow and Beijing to endorse a weakly worded resolution with no deadline for Iran’s cooperation and no warnings of penalties if it doesn’t.
But it once again stalls attempts to probe the allegations and signals Iran that it can thumb its nose at the world community.
The big power split along East-West lines is not new - but it is becoming more of a problem for Washington and its allies as Tehran advances in enriching uranium, which can be used for making weapons as well as fueling reactors.
Tehran denies hiding a weapons program and insists its enrichment activities are meant only as an energy source.
But as Iran gets closer to bomb-making ability, Israel may opt to strike militarily rather than take the chance that its arch-foe will possess nuclear weapons.
Israeli officials have increased warnings that such a strike is being contemplated, and the U.S. also has refused to take that option off the table.
Israeli officials have suggested they could accept crippling Iran sanctions as an alternative to force.
But despite four rounds of economic sanctions, the United Nations is being held back from tougher measures by Russia and China, both of them veto-wielding Security Council members and bound to Iran by strategic and economic interests.
Moscow and Beijing have offered no sign of a change in posture since President Obama’s meetings Saturday with Russian President Dmitry Medvedev and Chinese President Hu Jintao.