Will "TM" Protect Mark?

Dear Rich: I was wondering if you could clarify the legal use of "TM."So if a word say "ABCSOMEBRAND" is a registered trademark since 10 years and is active, in use and not abandoned, is it okay for an unrelated third party to use a "ABCSOMEBRAND" TM, with a service that is similar to the registered mark? For example Party A registered a mark, and Party B starts using this same mark with TM and is competing with Party A. If you use a mark similar to a registered mark, for similar services, you're probably infringing. Placing the "TM" bug next to the mark won't shield you from a lawsuit. The "TM" simply means that the owner believes that mark is proprietary; it has no legal significance.