Iran risks losing influential friends - and giving foes long-sought leverage to haul it before the U.N. Security Council. But it seems ready to defy the world in its drive to master technology that could be used to make nuclear weapons.
The issue is uranium enrichment. Iran on Tuesday ended a voluntary freeze and prepared to start what it called small-scale separation of isotopes from uranium gas. Depending on the level of enrichment, the process results in either nuclear fuel or the fissile component of nuclear warheads.
Iran says it is in sync with the Nuclear Nonproliferation Treaty allowing nations to run peaceful atomic programs. But whereas Canada, Japan and a handful of other nations have carried out enrichment programs without a hint of controversy, Iran has hidden its activities for decades.
Tehran has turned to the same black market Libya shopped from in assembling basic elements of its now dismantled nuclear weapons program. It also separated plutonium and did other work that could be used to develop nuclear arms.
A nearly three-year probe of the International Atomic Agency has turned up no "smoking gun" - but plenty of munition for the United States and others that have long insisted Iran's nuclear activities are a front for a weapons program. They include drawings of what appear to be parts of missile warheads, imports of "dual-use" material - and the drive to make nuclear fuel through enrichment, even though Iran is rich in oil and natural gas.
Iran's record in helping clear up ambiguities also is spotty, leaving even Mohamed Elbaradei, the IAEA's soft-spoken head, exasperated.
ElBaradei has been key in Iran's efforts to trip up Washington and its allies in their efforts to have Iran answer to the Security Council because he commands great respect among the nonaligned members of the IAEA's 35-nation board. Such open criticism of Iran by ElBaradei is thus bound to work against Iran.
Even more crucial are Russia and China, both IAEA board members and voting members of the Security Council.
Their past opposition to Security Council referral has led the Americans and their backers to tread carefully. They did not want to end up having Iran hauled before the council only to be hamstrung because of vetoes from Moscow or Beijing.
The council would have a wide range of options which could extend to economic embargoes or diplomatic sanctions. But with Iran being OPEC's second-largest oil producer, it could probably work out behind-the-scenes deals to avoid economic damage.
There has been speculation that the United States or Israel might weigh an attack on Iranian facilities - but there are considerable political and tactical constraints. British Foreign Secretary Jack Straw said Tuesday he does not believe that military action is on any country's agenda.
U.S. officials say both Moscow and Beijing strongly urged Tehran to desist from resuming further enrichment related activity - and were chagrined when their appeals were ignored.
Britain's Straw said London was "profoundly concerned." German Foreign Minister Frank-Walter Steinmeier said Tehran had "crossed lines which it knew would not remain without consequences." French President Jacques Chirac said Iran - and North Korea - were in danger of committing a "grave error," according to the AP.
The Russian Defence Ministry harbours plans to build a deep-water submersible vehicle to reach the bottom of the Mariana Trench