The change is being caused by the expiration of the HEU-LEU contract, signed in 1993 by Russia and the US. The treaty, which expires in 2013, allowed the duty-free export of Soviet uranium extracted from nuclear warheads.
Weaponisation followed, with the manufacture of up to 200 chemical warheads for its Russian-supplied Scud-B and Scud-C missiles, as well as thousands of chemical free-fall bombs and artillery shells.