In his radio address Saturday, President Bush said, "We cannot afford to be without this law for a single moment."
However, Senate Minority Leader Harry Reid says Americans "live by a document called the United States Constitution that directs what we do." And the Nevada Democrat adds, "when we start saying security is more important than the liberties of the American people this country is in trouble."
Republican Jeff Sessions of Alabama says he's convinced "there's nothing in this legislation that in anyway jeopardizes the great liberties that we've had."
Texas Republican John Cornyn says it's "pure fantasy" to think the federal government has somehow decided to suspend the civil liberties of the American people in pursuit of terrorists.
Mr. Bush said Saturday that senators who are blocking renewal of the terrorism-fighting act are acting irresponsibly and standing in the way of protecting the country from attack.
The vote to advance the measure, 52-47, fell eight votes shy of the 60 votes required to end debate on Friday.
"That decision is irresponsible and it endangers the lives of our citizens. The senators who are filibustering must stop their delaying tactics and the Senate must reauthorize the Patriot Act," Bush said.
Opponents of renewing the law, most of whom are Democrats, argue that it threatens constitutional liberties at home.
Most Republicans and other supporters say the act is essential for protecting the country against terrorists. The law was enacted in the aftermath of the attacks of Sept. 11, 2001.
Of the 55 Republicans in the Senate, four helped to block its passage while two of the 45 Democrats pushed to pass it.
Some of the most contentious elements of the Patriot Act include powers granted to law enforcement agencies to gain access in secret to library and medical records and other personal data during investigations of suspected terrorist activity.
The law allows the government to conduct roving wiretaps involving multiple phones and to wiretap "lone wolf" terrorists who may operate on their own, without control from a foreign agent or power.
If the law is not renewed, its powers would expire Dec. 31 only for new investigations of people whose criminal activity began after Dec. 31 and who were not associated with anyone who was under investigation before Dec. 31.
No one says they want all the Patriot Act provisions to expire December 31, reports CBS News correspondent Bob Fuss, but with President Bush refusing to accept a short-term renewal to allow more negotiations that now appears likely.
Senate Majority Leader Bill Frist changed his vote at the last moment after seeing the critics would win. He decided to vote with the prevailing side so he could call for a new vote at any time. He immediately objected to an offer of a short term extension from Democrats, saying the House won't approve it and the president won't sign it.
"We have more to fear from terrorism than we do from this Patriot Act," Frist warned.
Sen. Patrick Leahy, D-Vt., and a chief supporter of the original Patriot Act, said in a statement after Bush's radio address that the administration and GOP congressional leaders rewrote the reauthorization in ways that fell short of protecting basic civil liberties and then attempted to force it through Congress.
Leahy urged Bush and GOP leaders to support a brief extension of the law so that changes could be made in the reauthorization.
"Fear mongering and false choices do little to advance either the security or liberty of Americans," Leahy said. "Instead of playing partisan politics and setting up false attack ads, they should join in trying to improve the law."
The debate over the Patriot Act was fueled anew by a New York Times report that Bush had secretly authorized eavesdropping on individuals in the United States without first gaining permission from the courts.
In his radio address, Bush defended his decision to authorize the National Security Agency to conduct the secret probes much as he defended the Patriot Act, saying both had saved lives and prevented more attacks.
Noting that key provisions of the Patriot Act are set to expire in two weeks, the president said: "The terrorist treat to our country will not expire in two weeks. The terrorists want to attack America again, and inflict even greater damage than they did on September the 11th."
Bush added, "Congress has a responsibility to ensure that law enforcement and intelligence officials have the tools they need to protect the American people."
If the Patriot Act provisions expire, Republicans say they will place the blame on Democrats in next year's midterm elections. "In the war on terror, we cannot afford to be without these vital tools for a single moment," White House press secretary Scott McClellan said. "The time for Democrats to stop standing in the way has come."