But a Democratic senator threatened a filibuster to block the compromise.
"I will do everything I can, including a filibuster, to stop this Patriot Act conference report, which does not include adequate safeguards to protect our constitutional freedoms," said Sen. Russ Feingold, D-Wis., who was the only senator to vote against the original version of the Patriot Act.
Senate Judiciary Chairman Arlen Specter, R-Pa., announced Thursday that a House-Senate negotiating committee had reached an agreement that would extend for four years two of the Patriot Act's most controversial provisions — authorizing roving wiretaps and permitting secret warrants for books, records and other items from businesses, hospitals and organizations such as libraries. Those provisions would expire in four years unless Congress acts on them again.
"All factors considered it's reasonably good, not perfect, but it's acceptable," Specter said of the agreement.
Also to be extended for four years are standards for monitoring "lone wolf" terrorists who may be operating independent of a foreign agent or power. While not part of the Patriot Act, officials considered that along with the Patriot Act provisions.
The Republican-controlled House had been pushing for those provisions to stay in effect as long as a decade, but negotiators decided to go with the GOP-controlled Senate's suggestion.
Most of the Patriot Act would become permanent under the reauthorization.
The White House applauded the agreement.
"The Patriot Act is critical to winning the war on terrorism," White House press secretary Scott McClellan said. "The president urges both houses of Congress to act promptly to pass this critical piece of legislation."
Feingold is not alone in his dislike of the compromise.
"We believe this conference report will not be able to get through the Senate," said a group of six senators, including Feingold, who have been working against the emerging deal. They said they will not support it in any form.
The other senators are Republicans Larry Craig of Idaho, John Sununu of New Hampshire and Lisa Murkowski of Alaska and Democrats Dick Durbin of Illinois and Ken Salazar of Colorado.
It takes 60 senators to overcome a filibuster in the 100-member Senate.
"I don't think there will be a filibuster," Specter said. "I don't think it will succeed if there is one."
Sen. John Cornyn, R-Texas, said the deal should satisfy everyone. "This agreement both preserves the provisions that have made America safer since 9/11 and increases congressional and judicial oversight, which should alleviate the concerns of those who believe the law enforcement tools endanger civil liberties," he said.
But the American Civil Liberties Union immediately denounced the deal, calling on lawmakers to reject the legislation because it intrudes too far into the privacy of innocent Americans.
"This sham compromise agreement fails to address the primary substantive concern raised by millions of Americans, as well as civil liberties, privacy and business organizations and lawmakers from both sides of the aisle and in both chambers," said Caroline Fredrickson, the ACLU's Washington legislative office director.
The ranking Democrat on the Senate Judiciary Committee, Patrick Leahy of Vermont, has not yet decided whether to support the agreement, a spokesman said. But the GOP-majority negotiating committee has enough votes to send the House and Senate the compromise if all of the Republican negotiators agree to it.
The Senate is expected to vote on the compromise next week, Specter said. That would give them enough time to deal with any filibuster threats before the Patriot Act provisions expire on Dec. 31.
Congress overwhelmingly passed the Patriot Act after the Sept. 11 terrorist attacks. The law expanded the government's surveillance and prosecutorial powers against suspected terrorists, their associates and financiers.
The compromise also makes changes to national security letters, an investigative tool used by the FBI to compel businesses to turn over customer information without a court order or grand jury subpoena.
Under the agreement, the reauthorization specifies that an NSL can be reviewed by a court, and explicitly allows those who receive the letters to inform their lawyers about them.
The Bush administration contends that such consultation already is allowed, citing at least two court challenges to NSLs. However, in a letter obtained by the ACLU under the Freedom of Information Act and posted on its Web site, the FBI prohibits the recipient "from disclosing to any person that the FBI has sought or obtained access to information or records under these provisions."