CNN) -- The federal government Friday launched a national "do-not-call" registry aimed at stopping most telemarketing phone calls to people who regard the sales pitches as invasive and want them blocked. By 2:30 p.m. EDT 635,000 phone numbers had been registered, the Federal Trade Commission said. Officials said they expect 60 million people to register eventually.

Consumers can join the registry online at http://www.donotcall.gov or by phone west of the Mississippi River (1-888-382-1222). Some Internet users reported trouble accessing the site on Friday, presumbly because of heavy traffic. Nationwide registration by phone will be available next month. "When Americans are sitting down to dinner or a parent is reading to his or her child the last thing they need is a call from a stranger with a sales pitch," President Bush said at a White House ceremony inaugurating the project. "So we are taking practical action to address this problem." Charities, surveys and calls on behalf of politicians are exempt from the registry.