Anhydrous ammonia (281410) is pure NH₃ in gaseous or liquefied form, while aqueous ammonia (281420) is ammonia dissolved in water at varying concentrations. Beyond the classification split, anhydrous ammonia carries a more stringent regulatory burden as a toxic inhalation hazard under DOT and EPA RMP rules, whereas aqueous solutions at lower concentrations face less restrictive transport requirements.

Both countries have large natural gas reserves and have invested heavily in world-scale ammonia production facilities that use natural gas as feedstock. Their cost-competitive production and proximity to US Gulf Coast import terminals make them reliable sources, particularly when North American supply is constrained by pipeline logistics or seasonal agricultural demand peaks.