(Stars And Stripes) — U.S. military officials say they can trace to Pakistan a vast majority of the chemicals used to construct makeshift bombs that are proving most deadly for U.S. and coalition forces in Afghanistan, USA Today reports.

The connection is yet another barb in an increasingly tense relationship between the United States, which has accused Pakistani officials of abetting insurgents, and Pakistani officials who deny the accusations.

More than 80 percent of the improvised explosive devices, or IEDs, are made using calcium ammonium nitrate fertilizer that is made in Pakistan, USA Today reports.

Between June and August, U.S. troops detected or were hit by 5,088 IEDs that killed 63 troops and wounded 1,234, USA Today cites Defense Department records.