A group of five Republican senators is seeking a delay in legislation, supported by several large tech vendors, that would overhaul the U.S. patent system.

The five, including Senators Chuck Grassley of Iowa and Sam Brownback of Kansas, have asked for more hearings before the Senate Judiciary Committee moves ahead with the Patent Reform Act, which is scheduled to be amended and approved in a Thursday hearing. The five sent a letter Monday to the Judiciary Committee asking for more hearings.

"Many prominent American businesses on the cutting edge of innovation are expressing concerns about the impact of sweeping patent reform," said the letter, also signed by Senators Tom Coburn of Oklahoma, Jon Kyl of Arizona and Jeff Sessions of Alabama. "These concerns merit thoughtful deliberation."

Many observers have called the Patent Reform Act the most sweeping reform of U.S. patent laws in decades. The bill would make it tougher for inventors to obtain new patents, make it easier to challenge patents, and reduce the legal penalties for patent violations.

Microsoft Corp., Cisco Systems Inc. and IBM Corp. have praised the bill, saying it's too easy for the owners of questionable patents to sue tech companies and collect large damages or shut down entire product lines with court injunctions when one small piece of a product allegedly infringes a patent.

"This important measure ensures that our patent system continues to foster innovation and economic growth by promoting improvements in patent quality [and] discouraging litigation abuse," Microsoft said in a statement when the bill was introduced.

But five Republican senators raised concerns about the bill, echoed by some small tech companies and other members of the Coalition for 21st Century Patent Reform, a group calling for less sweeping changes to the U.S. patent system.

The senators questioned the bill's attempt to apportion patent award damages. The bill would limit the damages a patent holder can collect when an infringing technology is part of a larger product, based on the value of the patented technology itself, instead of the value of the larger product. Courts now generally consider the value of the larger product when assessing damages.

The senators also questioned the bill's provisions to allow new ways to challenge patents after the U.S. Patent and Trademark Office has granted them.

These changes "need to be more carefully examined to ensure that they do not undermine innovation, increase frivolous litigation, or undermine property rights," the letter said.

The letter also calls on the committee to look harder at ways to improve patent quality.