In 2003, Iran is believed to have done work on a trigger for a nuclear weapon at a military complex called Parchin.
Inspectors from the International Atomic Energy Agency went there in 2004 and were unable to find anything, but it's a very large complex, and the IAEA wants to go back and take another look.
Iran has turned down two recent requests for IAEA inspectors to visit, but now satellite imagery has revealed what some analysts believe is earth moving activity at the site - as if they were trying to remove contaminated soil that might contain traces of radiation.
The suspicion is, of course, is that if Iran now relents and lets inspectors into the area, there will be nothing left to find.
Meanwhile, Obama administration officials insist there was no "deal" reached for Israel to be supplied with more weapons from the U.S. in exchange for them delaying an attack on Iran, as has been reported.
If, however, Israel requests more bunker buster bombs, or air tankers, from the U.S. they will almost certainly get them.
The more capable a strike Israel can launch - if they do launch one - the longer they may be willing to wait to actually launch it, and the longer they wait, the longer sanctions have a chance to wait. That falls in line with the Obama administration's objective, which right now is a preference for anything over a military strike.Click on the player above to see David Martin's full report on the standoff with Iran over its nuclear program.