From FP Situation Report (in an email) and not a great surprise I'd wager:
But Lt. Gen. Mike Barbero, the head of JIEDDO, tells Situation Report he struggles with one thing that is much harder to control: stopping the flow of ammonium nitrate, used to make the overwhelming majority of the home-made explosives used against troops in Afghanistan, from entering the country from Pakistan.

Home-made explosives account for 83 percent of IED "events," defined as found, cleared or detonated, and of that, 72 percent is made with ammonium nitrate. One bag of it can produce seven or eight IEDs, he said. "It's a supply issue," Barbero said.

The problem is not new. But there is increasing frustration among American officials that the Pakistanis seem unwilling to help do anything about the problem. "They can and need to do more....The bottom line is, I know they could do more, it is an area so open for cooperation."

Among other efforts to slow the flow of the ammonium nitrate, Barbero has asked Pakistani fertilizer supplier FATIMA to add dye to their product, a relatively low-cost additive that will help border guards between Afghanistan and Pakistan identify the bags as bomb-making material. Even with an extremely porous border, that could make it harder for insurgents to transport the material, Barbero says. But efforts to get the Pakistani government to push the firm into adding the dye have not been successful, Barbero says.
"On the network and IED cooperation point there has been a lot of talk about cooperation with us, but there hasn't been any real cooperation," Barbero said of the Pakistanis.