A majority of Republicans on the Senate Judiciary Committee have voiced serious concerns to the panel's leaders about components of a bill to overhaul the U.S. patent system.

Sens. Tom Coburn of Oklahoma, Charles Grassley of Iowa, Jon Kyl of Arizona; Jeff Sessions of Alabama and Sam Brownback of Kansas sent the letter Monday to Judiciary Chairman Leahy and ranking member Arlen Specter, R-Pa. The move came less than a week after a panel hearing to discuss the legislation.

Those lawmakers concerned about the bill said "it is important to update our nation's patent system to ensure better patent quality and to preserve property rights in the inventions that drive our economy." But the hearing showed "there are multiple issues that need to be reviewed and discussed" before the bill gets a committee vote, they said.

Patent and Trademark Office Director Jon Dudas, as well as stakeholders from large and small technology companies, a biotechnology firm and the financial sector testified at last Wednesday's hearing. The bill is scheduled for action Thursday, but the panel routinely holds agenda items.

Further discussion is needed among members, staff, the PTO, the Justice Department and industry players, the senators wrote. A staffer for one of the signatories emphasized that it was not his boss' intention to "kill the bill."

Some members planned to ask follow-up questions to hearing witnesses, and the committee should have time to review their responses, the letter said. "It is likely that those answers will give insight into changes that should be made."

The lawmakers said more hearings are needed to tackle perceived deficiencies in the legislation.

The attendance record for the panel's patent hearings by those who spoke out is poor. Coburn was the only one at last week's hearing and at one in May on so-called process patents. None attended several hearings in the 109th Congress.

The letter said certain provisions should be studied "to ensure that they do not undermine innovation, increase frivolous litigation, or undermine property rights." The proposals include mandatory apportionment of damages, whereby money is given to the successful party in a patent feud; post-grant opposition of patents, and broad PTO rulemaking authority.

More attention should be given to improving patent quality and reducing costly litigation, the letter said.

Gary Griswold, president and chief IP counsel for 3M, said it is "critical that the proposed reforms are thoroughly vetted and reviewed." When paired with recent Supreme Court rulings, portions of the bill could undermine incentives to innovate, he said.

Ken Johnson, senior vice president for the Pharmaceutical Research and Manufacturers of America, said he was pleased to see the letter because the Senate measure and its House companion would weaken protections afforded to patent holders.

But the Coalition for Patent Fairness, which represents major technology and media companies, said "years of hearings and study" have led to this bill, and its sponsors believe it is time to act. "Now is not the time for delay," spokesman Mark Isakowitz said.