As companies battle over control of the technology used in some of the hottest devices and websites, leaders of the Senate Judiciary Committee say they fear patents could be used to stifle competition.

Rather than resolving patent disputes in court, some companies may use trade laws to inappropriately block other companies' patents, Judiciary Chairman Patrick Leahy, D-Vt., and Judiciary Antitrust Subcommittee Chairman Herb Kohl, D-Wisc., said in a letter to the Justice Department on Thursday.

Tech giants like Apple, Microsoft, and Google have increasingly sought to protect their businesses by buying up troves of patents; acquiring other companies; and launching legal battles.

Yahoo, for example, is taking Facebook to court over alleged patent infringement.

But some practices could be anti-competitive, Leahy and Kohl warned. Asking the International Trade Commission to completely block use of a certain patent, rather than working out a compromise, poses "a significant threat to competition and innovation," the lawmakers wrote.

The Justice Department raised the concern when it approved Google's plan to buy Motorola in February. The department also approved requests from Apple, Microsoft, and Research in Motion to buy patents from Nortel.

Leahy and Kohl said they had no position on the deals but said they highlight the potential for companies to use patents against each other. They urged the department to be "vigilant in monitoring the anti competitive use" of patents.