Opponents, namely biotech and pharmaceutical firms, claim the bill would undermine current patent protections and deter investors from taking chances with innovative ideas.

The pending legislation has had support from Microsoft, Cisco, Intel and other big tech firms. It is designed to control excessive litigation; however, detractors claim it would benefit large corporations at the expense of startups.

Inventors and CEOs from more than a dozen companies said they object to the provision that would permit companies to challenge patents after awarded in a subsequent review process.

At a briefing Thursday, several executives said they were concerned that because the esoteric, technical details of patent law are difficult to understand, a bad bill might get through Congress.

Rep. Howard Berman (D-CA), a chief sponsor of the House bill, said he would continue to "tweak" provisions when Congress negotiates the details of a final bill.