ICANN, a nonprofit organization, approved a plan in June to allow for the registration of new domain names in addition to traditional domains such as ".com" or ".org." Beginning in 2012, organizations can register new addresses ending in almost any word or phrase.
In the letter, the advertisers said the plan would force companies to spend thousands of dollars buying up new domain names to protect their brands.
The letter also warned that the Internet would become a "veritable minefield for criminal activity" because scammers could lend themselves legitimacy with domain addresses ending in trusted brand names.
"Just know that we are directly and forcefully communicating that the path ICANN is taking has been flatly rejected by American businesses and industry," Liodice wrote.
The letter disputed ICANN's arguments that the new system will increase competition, relieve scarcity in domain name space and allow for differentiation between services and products.
The ANA did not rule out litigation over the issue.
"Should ICANN refuse to reconsider and adopt a program that takes into account the ANA's concerns expressed in this letter, ICANN and the Program present the ANA and its members no choice but to do whatever is necessary to prevent implementation of the Program and raise the issues in appropriate forums that can consider the wisdom, propriety, and legality of the Program," Liodice wrote.
ICANN declined to comment on the letter.
This post was updated at 4:32 p.m.