WASHINGTON  Federal law enforcement and national security officials are preparing to seek sweeping new regulations for the Internet, arguing that their ability to wiretap criminal and terrorism suspects is “going dark” as people increasingly communicate online instead of by telephone.

Essentially, officials want Congress to require all services that enable communications  including encrypted e-mail transmitters like BlackBerry, social networking Web sites like Facebook and software that allows direct “peer to peer” messaging like Skype  to be technically capable of complying if served with a wiretap order. The mandate would include being able to intercept and unscramble encrypted messages.

The bill, which the Obama administration plans to submit to lawmakers next year, raises fresh questions about how to balance security needs with protecting privacy and fostering innovation. And because security services around the world face the same problem, it could set an example that is copied globally.

James X. Dempsey, vice president of the Center for Democracy and Technology, an Internet policy group, said the proposal had “huge implications” and challenged “fundamental elements of the Internet revolution”  including its decentralized design.