From the beginning, the Patriot Act, which allows wiretaps and other surveillance, has been dogged by concerns that it represented a government power grab that could violate people's rights against unreasonable searches and seizures.

But the White House is urging the Senate to speed up its typically slow pace and pass the extension by mid-week.

The deadline is especially tight because Obama is in Europe. Any extension passed by the Senate must be sent to the House and passed there, then flown overseas to be signed into law.

The legislation would extend three expiring provisions until June 1, 2015. These provisions would allow the government to use roving wiretaps on multiple electronic devices and across multiple carriers and get court-approved access to business records relevant to terrorist investigations.

The third, a "lone wolf" provision, permits secret intelligence surveillance of non-US individuals without the government having to show a connection between the target and a specific terrorist group.

"It is essential to avoid any hiatus" in the law's powers, the Obama administration said in a statement.

Senate majority leader Harry Reid, a Democrat who not long ago vowed to have a full week of debate on the Patriot Act extension, has instead backed up the vote against a tighter deadline to limit debate over legislation some say is less necessary now that Al-Qaeda chief Osama Bin Laden is dead.

But the Senate does not rush, even when it's clear that there probably isn't time for changes. Senators voted 74-8 on Monday to begin debate on the bill.

Members of both parties demanded time to talk about their amendments, some of which would require tougher oversight on how the government uses the law's powers. Reid was negotiating on Monday on which amendments would be considered, and for how long.

Opposition has come from an unlikely alliance of libertarian-leaning conservatives and liberal Democrats who on Monday said they would join forces to limit the law's power. Some Patriot Act opponents have suggested that in this post-Bin Laden world it's time for Congress to reconsider the act, written when the terrorist leader - killed earlier this month at his Pakistan home by US Navy SEALs - was at the peak of his power.

"We were so frightened after 9/11 that we readily gave up these freedoms," said Republican Sen. Rand Paul. "We really should sunset the entire Patriot Act and protect our liberties the way it was intended by our founding fathers." But the act's supporters warn that Al-Qaeda splinter groups, spread from Pakistan to the United States and beyond, may try to retaliate for Bin Laden's death.

"We are not out of harm's way, and no one should believe that," said Senate Intelligence Chairwoman Dianne Feinstein, a Democrat.