Chasing News That Isn't News
The Latest Scare Story About Iran: Missiles Targeting US by 2015
However, you'll look in vain for any such statement in the BMDR itself. What you'll find instead is the assessment, repeated several times, that:
That's rather less of a scary story than in the unclassified version of what the DoD sent to Congress about Iran. It is from this document (PDF) that the scary statement is taken. And even then, it isn't all that scary. It says (emphasis mine):
Back to the BRDM itself, in which we find the telling line:
Russia and China are also the only two of Iran's allies, even fringe allies, that possess the technology to produce ICBMs. That means the "sufficient foreign assistance" would have to come from one of those nations, either directly or via a third party like North Korea. Yet that seems unlikely given that both are "important partners for the future" of the United States. Both must know that giving ICBM technology to North Korea or Iran would scuttle that relationship - and there are no other candidates for that "sufficient foreign assistance"
Also, remember: "the United States possesses a capability to counter the projected threat from North Korea and Iran for the foreseeable future." That's even if they were to get such "foreign assistance", presumably from Martians.
The mainstream media (and probably Congress) have fallen for it hook, line and sinker - but what we have here is a scary story designed to keep the missile defense procurement budget topped up by telling scary stories and hyping possible war. Nothing more.
UPDATE: The Arms Control Wonk explains that "could" actually means "not likely".
Dr. Lewis also notes that the same "With sufficient foreign assistance" sentence "has appeared in every edition of Ballistic and Cruise Missile Threat: 2009, 2006, 2003 and 2000. Seriously, you can look it up." His conclusion is that the press are chasing news that isn't anything new at all.