BRUSSELS — A dispute between Chinese and Indian airlines and Europe over greenhouse gas rules could be a precursor to broader international resistance to the European system at a global conference later this year in Montreal.

Starting in late September, the International Civil Aviation Organization, a United Nations agency, will supervise discussions in the Canadian city, during which the European system is expected to meet severe criticism from many other nations.

Without an agreement on a global system, the European Union may have to drop the airline component from one of its signature projects: its effort to lead the world in controlling the emission of greenhouse gases, which are linked to global warming.

To head off that humiliating prospect, senior European officials have already been courting support from the United States.