Registration may be used worldwide to prevent importation of infringing foreign goods. A domain name is the your personal or business identity online. Depending on the factual situation, the Trademark Office may or may not be the proper forum. You should consider contacting an attorney, preferably one specializing in trademark law. Local bar associations and the yellow pages usually have attorney listings broken down by specialties.
Time can be of the essence.
Names you use in commerce are very valuable assets that you need to protect. A domain name is sometimes used as an Online Name identifying a registered user of an i-mall or auction. However, keep in mind that a domain name in itself does not automatically confer a trademark on the domain name. Protection of your domain name is even more important if it does not end with dot-com, which suggests that someone else registered the same name ahead of you. You don't want others to be using your identity on another site.