For over a year, top military leaders have been quietly conducting a charm offensive in Silicon Valley, in hopes that the tech industry might want to work with the Pentagon again like it used to during the Cold War. A lot has changed since then; some in tech don't want to be seen as being too close to the U.S. government for fear of alienating international customers in a globalized world.

Still, Defense Secretary Ash Carter seems determined to rebuild that relationship, making trips out to California, founding a new office meant to get cutting-edge tech into the hands of soldiers and meeting everyone from Facebook to Andreessen Horowitz, one of the Valley's signature venture capital firms.

Now one of the partners at Andreessen Horowitz says he's diagnosed a huge challenge that the Pentagon will have to overcome if it wants to woo the tech industry back.

"You hit a product cycle problem," said Martin Casado, a former Defense Department researcher who is one of nine partners at the firm, at a Washington conference Friday. "The procurement cycle is too baroque."

Casado's putting a finger on a choice that he says faces every start-up that wants to sell its goods to the military, be it software or hardware. At some point, the bureaucratic demands placed by the military on private-sector suppliers become so complicated that tech companies can either 1) stop chasing after government contracts so that they can keep selling to regular consumers like you or me, or 2) agree to focus all their energies on the government, effectively making the Pentagon their only customer.

"If the companies decide to sell into the government, that's basically all they do. You wind up building government-only companies, which is not what we want. What we want are base technologies that are very consumable by everybody," Casado said.

There are obvious outliers to this model. Many contractors in the aerospace industry, for instance, serve both government and commercial clients. So do firearms manufacturers. But military contracts can make up a huge chunk of (reliable) income for many businesses in this position — even food vendors. So the incentive to become a "government-only" company, to use Casado's phrase, is strong.

Chances are this isn't what Carter wants out of the tech industry, either — the whole point is that private-sector innovation has outpaced government. It would be self-defeating for the military to turn around and make vassals out of the companies that are creating what's around the bend. So that's where all the emphasis on public-private partnerships comes from.

Still, that doesn't mean there aren't vastly different cultures in play here. And if Casado is right, the Pentagon may need to rethink how it does contracting to make it work for Silicon Valley. Some parts of the Defense Department are already doing this. Camron Gorguinpour is an Air Force official who leads an office that's looking to cut the amount of time it takes to get new contracts signed from years to a matter of weeks if not days. The two-year-old department is looking at ways to do business smarter and faster.

"We're kind of like the skunkworks for bureaucrats," he joked at the conference.