For years, there has been considerable debate within the intelligence community regarding Iran’s purchase of the S-300 air defense system from Russia. While reports of a pending deal never quite panned out, analysts universally agreed that Tehran was interested in the system. Not only would the S-300 fill a critical air defense gap, it would force adversaries (read: the U.S. and Israel) to reconsider attack plans.

The missile purchase apparently moved from the “possible” to the “inevitable” category late last year, after senior U.S. defense officials said that a deal had been concluded. It was the highest confirmation to date that Iran would acquire the S-300, echoing similar claims in the defense press and Russian media circles.

But other sources reported that the contract had not been signed. In February, Reuters claimed that Iran’s defense minister made a pitch for the air defense system during a visit to Moscow, suggesting that earlier claims were premature, downright false, or the “deal” had been pre-empted by other events. Officials in Washington suggested those “events” might be some sort of “missile swap,” with the U.S. trading its planned missile defenses in Eastern Europe for Russian help on the Iranian nuclear issue–and cancellation of the S-300 transfer to Tehran.

While that sort of trade is straight out of the Obama playbook, we expressed grave doubts about that scenario. The air defense deal was worth too much money (well over $1 billion) and besides, Moscow probably believes that Mr. Obama will gut our missile defense programs, without any significant concessions on their part. For those reasons, a “swap” was highly unlikely, and sure enough, new information supports that assessment.

According to the Associated Press, a senior Russian defense official has confirmed that an S-300 deal with Iran was signed more than two years ago, but the weaponry has not been delivered. The official disclosed that development in conversations with Russian reporters. He did not say why that contract remains unfulfilled, but suggested that completing the transfer will depend “on the current international situation and the decision of the country’s leadership.”

There are also suggestions that Russian President Dmitry Medvedev will use the missile deal as a potential bargaining chip in next month’s meeting with President Obama. But that ignores Mr. Medvedev’s previous comments on the matter; barely two weeks ago, he said there would be “no haggling” over the nuclear issue (and, we presume, the S-300 sale). Medvedev’s remarks came in response to a report in The New York Times, outlining a missile swap proposal from Mr. Obama to his Russian counterpart.

Despite the delay, it seems almost certain that S-300 deliveries to Iran will begin in the not-too-distant future. In fact, there are probably other reasons for the deferred delivery, ranging from Iran’s legendary reputation for slow payment, to the change of political leadership in Washington. There’s also the possibility that Iran is simply waiting its turn in the production line, behind customers like China that have made significant purchases of the air defense system.

There’s one more factor that may influence the delivery schedule–the recent change of government in Israel. With the conservatives now in charge, Tehran is undoubtedly clamoring for the S-300, as a hedge against a potential Israeli air strike. With air deliveries and Russian contractors at the controls, Iran could establish an initial operating capability in a matter of weeks, rather than months.

If the AP report is accurate, the S-300 deal has been “on” for some time, it’s just a matter of delivering the hardware to Tehran, and training Iranian crews. That’s why we still believe the advanced SAM system will appear in Iran sometime this year, and there’s little that Mr. Obama can do (or perhaps we should say, is willing to do) in altering that timetable.