This paper analyzes how a reduction in trade costs influences the possibility for firms to engage in international cartels, and hence how trade liberalization affects the degree of competition. We consider a particular intra-industry trade model amended to allow for firms producing differentiated products. Our main finding is that trade liberalization may have an anti-competitive effect. We find that there is no unique relation between a reduction in trade costs and the degree of competition. When products are differentiated, a lowering of trade costs is pro-competitive if trade costs are initially high, but anti-competitive if trade costs initially are low. Hence, trade policy is not necessarily a substitute for competition policy