The rise in violent cellphone thefts is increasing pressure from Congress for phone companies to add an anti-theft kill switch feature on tablets and smartphones, so a group of businesses made a voluntary pledge to add such technology to phones sold in the U.S. by July 2015.

Four Democratic senators including Sens. Amy Klobuchar, D-Minn., and Barbara Mikulski, D-Md., have introduced a bill to require wireless companies to install a “kill switch” feature allowing users to erase and shut down stolen devices, following up on a bill introduced by California state lawmakers in Sacramento.

[READ: Congress Joints the Smartphone Kill Switch Fight]

To preempt regulation a group of companies on Tuesday agreed to voluntarily add “at no cost to consumers, a baseline anti-theft tool that is preloaded or downloadable on wireless smartphones,” according to a news release from CTIA, a trade association for the wireless industry. The tool will be able to erase data from a lost or stolen phone, disable a stolen device, prevent reactivation without a user's permission, and restore the operability of the phone if it were recovered, according to the agreement.

The CTIA has opposed the mandatory addition of cell phone kill switches in the past for fear it could create a “trap door” that could be exploited by hackers, as reiterated in the news release from Steve Largent, president of CTIA.

“This flexibility provides consumers with access to the best features and apps that fit their unique needs while protecting their smartphones and the valuable information they contain,” Largent said.

[ALSO: Mikulski Says Cellphone Kill Switch Fears are Baseless and Conspiratorial]

More than a dozen device makers, software companies and phone carriers have signed the voluntary agreement, including Apple, AT&T, Google, HTC, Motorola Mobility, Microsoft and Verizon Wireless.

This voluntary action is a positive step but it does not go far enough, said a joint statement from supporters of the California bill, New York Attorney General Eric Schneiderman and San Francisco District Attorney George Gascón.

"We strongly urge CTIA and its members to make their anti-theft features enabled by default on all devices, rather than relying on consumers to opt-in," they said. "The industry also has a responsibility to protect its consumers now and not wait until next year."