The September deadline set by President Obama for Iran to restart talks about its nuclear program is upon us.

The president said in July that the world couldn’t “wait indefinitely” and allow Iran time to develop a nuclear weapon. If Iran didn’t engage by September, Obama said, “further steps” would be needed.

Israel, whose existence is regularly denounced by Iranian leaders, is pushing for harsher sanctions (and maybe military action). Congress is weighing passage of the Iran Refined Petroleum Sanctions Act, which would punish countries that supply Iran with 40 percent of its gasoline and diesel.

But given the incredible political drama that has been playing out in Tehran since rigged June elections, the White House and Congress need to rethink earlier deadlines. Iran’s political elite is still convulsed in internal power struggles, whose results aren’t clear yet. The worst thing the administration could do would be to take action that strengthens Iran’s ultra-hard-liners while making the United States look weak.

To understand Obama’s options, it’s necessary to look backward. Before the disputed Iranian elections, the Obama team sent a letter to the country’s supreme leader, Ayatollah Ali Khamenei. The letter reportedly laid out a framework to resolve the question marks over Iran’s nuclear program and establish cooperation on regional issues.

The letter was in keeping with Obama’s campaign pledge to “engage” with Iran to reshape relations. Unconfirmed reports say the Iranians responded without commitment.

Then came Iran’s presidential elections, whose rigging sent millions of protesters into the streets. No further response has arrived from Iran since the vote, say top U.S. officials. Indeed, it isn’t even clear at this point who really controls security policy in Tehran.

What is clear is the vicious struggle for power going on within Iran’s ruling circles. An astonishing show trial is in progress targeting scores of intellectuals, along with political reformers (whose leaders were cheated of victory in the balloting). The whole affair, in which the accused make televised “confessions” of conspiring to counterrevolution, looks like something out of the 1950s Soviet Union.

Last week, Khamenei, whose word is supposed to be final, rebuffed efforts by hard-line Revolutionary Guards officials to portray top reform leaders as Western tools, and prosecute or even execute them. The very next day President Mahmoud Ahmadinejad, the election “victor” and front man for the Rev Guards militia, said those political leaders should be tried.

“Ahmadinejad’s remarks are virtually a slap in the face of Khamenei,” said Abbas Milani, director of Iranian Studies at Stanford University. We don’t know whether Khamenei will cave, he said, permitting the Revolutionary Guards to carry out a virtual military coup and take charge of security policy. Nor do we know how Khamenei will react if reformist leaders refuse to give up their cause or to drop charges that imprisoned protesters have been tortured and raped.

Either way, the supreme leader’s strength will be weakened. And, given internal fissures within the Revolutionary Guards and the conservative camp, there is an outside possibility that Ahmadinejad may be forced out.

None of this guarantees a change in Iran’s nuclear policy: All political leaders support Tehran’s nuclear program in public. However, the internal Iranian political turmoil has several key implications for Obama’s Iran policy.

“Any attempt to negotiate with them at this moment is futile,” Milani said. That’s because we don’t know who is really in charge of nuclear policy or who will be in the future.

The Iranian regime may agree to talks in order to stall. But, Milani said, such talks won’t yield results because a government in convulsion cannot make decisions. Moreover, should the West renew such talks while Iran’s internal struggle continues, this may be construed as a betrayal by Iranians who voted and protested for change.

If prospects for useful engagement appear nil, pressure will increase on Obama to pursue “crippling sanctions” against Iranian gas imports. Yet, here again, when seeking a policy that is likely to be effective, it’s necessary to consider internal developments in Iran.

Most Iran experts say they believe a gasoline embargo would be counterproductive if it’s backed only by the United States and some European nations. “These kind of sanctions, if they are unilateral, only help solidify the regime,” Milani said, by reunifying conservatives around their hostility to Western nations.

Unless sanctions are backed by the U.N. Security Council and adhered to by most nations, the Iranians will circumvent the cutoff. However, international sanctions will require much more intensive U.S. diplomatic efforts to win Russian and Chinese backing. The effort is worth making, but it will take more time.

The pressure on Obama to act quickly and set Iran deadlines comes from the perception that the nuclear clock is ticking as Iran moves toward acquiring the knowledge and materials for a bomb.

But Iran’s internal Iran clock is also ticking. A struggle is under way that could produce political outcomes more conducive to preventing an Iranian bomb. A weakened Iranian regime, hurt by lower oil prices, may be more willing to deal. An open military dictatorship, with aggressive regional goals, will arouse more global opposition.

Either way, it makes sense for Obama and Congress to wait until the dust settles. U.S. officials can work on Russia and China, meantime, to endorse tougher sanctions if they are needed later. But the best hope for halting Tehran’s nuclear program may lie with events inside Iran.