If US allies balk at sanctions, it's harder, but not impossible, to slap Tehran for nuclear aims.
Iran may yet end up on the docket of the United Nations Security Council for restarting its nuclear-fuel program. But even if the international community can agree to punish it with economic sanctions, will those actions succeed in stopping Tehran's pursuit of nuclear technology - and possibly a bomb?
Many doubt the current diplomatic efforts will have the desired effect, prompting some officials and analysts to lay out a range of Plan B's for coping with the crisis.
For some experts, the time is ripe to prepare the world economy for living without Iranian oil - by developing pipelines in the oil-rich Gulf region to circumvent Iran- dominated transport routes. With global markets already hinting at the impact that action against Iran could have, some say that countries should take steps now to ease the burden of future moves.
For others, the best course may be to accept that Iran is likely to develop a nuclear weapon eventually - and to prepare the region and the world for "the day after."
"I'm not saying I think a nuclear Iran should happen, but I think it's going to happen, so we have to prepare for that and deal with it," says Leon Hadar, a foreign-policy expert at the Cato Institute in Washington.
Recalling similar doomsday scenarios that greeted China's announcement that it had developed nuclear weapons, and global consternation eight years ago when Pakistan joined the nuclear club, Mr. Hadar says an argument can be made that even "rogue" regimes evolve once they possess the bomb.
"You can argue that [China's] behavior since it acquired nuclear weapons became more responsible," he says. The nuclear standoff between India and Pakistan has played a role in those two longtime enemies avoiding war over Kashmir, Hadar says. He adds that a similar understanding of "mutually assured destruction" might one day have to be developed between Israel and a nuclear Iran.