Attempts by tobacco-producing nations to sink a landmark law in Australia requiring plain packaging for cigarettes and cigars gained pace Tuesday as Cuba and the Dominican Republic stepped up their fight at the World Trade Organization. The WTO said that its disputes settlement body would on April 25 hear formal requests from both countries for the establishment of a panel to assess whether the Australian legislation breaches the rules of global commerce. Australia has faced a raft of challenges to its law, passed in 2011 and in force since December 2012, which politicians hope will curb the number of smokers and thereby improve public health. Under the rule, tobacco products have to be sold in drab green boxes, use the same typeface and contain graphic images of diseased smokers. Along fellow plaintiff Honduras, Cuba and the Dominican Republic say that by covering all tobacco products, not just cigarettes, the legislation harms their traditional cigar brands. Also involved in the WTO case are Indonesia and Ukraine, both of which are leading raw tobacco and cigarette exporters. The five countries argue that the law breaches international trade rules and the intellectual property rights of brands -- a stance rejected by Australia's government and which also failed to convince the country's High Court in a case brought by tobacco firms. The Geneva-based WTO ensures that its 159 members respect the rules of global commerce. Its dispute settlement process can last for years, amid appeals, counter-appeals and assessments of compliance. If its disputes panel of independent trade and legal experts finds against Australia, it has the power to authorise retaliatory trade measures by the wronged countries. Expert panels have already been given permission to hear the Ukrainian, Honduran and Indonesian complaints.