A bipartisan group of U.S. senators, demanding increased protection of civil liberties, defied President George W. Bush on Friday and blocked legislation to renew the USA Patriot Act, a centerpiece of his war on terrorism.

On a Senate vote of 52-47, mostly Republican backers of the measure fell eight short of the needed 60 to end debate and move to passage of it.

Proponents of the legislation warned that much of sweeping anti-terror law was to expire at the end of the month, and if it did, the nation could be placed at increased risk.

“We have a clear choice before us today: Do we advance against terrorism to make America safer or do we retreat,” Senate Majority Leader Bill Frist, a Tennessee Republican, said shortly before the vote.

Senate Democratic and Republican foes of the proposed renewal said the law could be swiftly reauthorized if lawmakers agreed to better balance national security with civil liberties.

“None of us wants it to expire, and those who threaten to let it expire rather than fix it are playing a dangerous game,” said Sen. Patrick Leahy, a Vermont Democrat.