A prominent Democrat has asked the US Senate to censure President George W Bush over a wiretapping scheme approved by him soon after the 9/11 attacks.
The Bush administration says it needs to act fast against terrorism
The unusual request was tabled by Senator Russ Feingold of Wisconsin.
Mr Feingold alleges Mr Bush violated the constitution when he ordered wiretapping without warrants but the White House denies the law was broken.
The BBC's Justin Webb says the motion has no chance of passing in the Republican-controlled Senate.
It is, however, a sign that the Democrats think the president is increasingly vulnerable, our correspondent adds. A censure resolution has been used only once before - against President Andrew Jackson in 1834.
As he introduced the motion, Mr Feingold told senators Mr Bush had "done wrong".
"The president violated the law, ignored the Constitution and the other two branches of government and disregarded the rights and freedoms upon which our country was founded," he added.
The existence of the wiretapping scheme was revealed by the New York Times in December.
Under the programme, the National Security Agency (NSA) was allowed to monitor the international calls and e-mails of a terrorist suspect inside the US without obtaining permission from a court.
The NSA is normally required to get a special warrant before it monitors someone inside the country.
The Bush administration argues it needs to find new ways to combat terrorism, taking all possible steps to locate suspects and know what they are plotting before they strike.
Senator Feingold says what the president did by consciously and intentionally violating the constitution and the laws of the country with his illegal wiretapping had to be answered.
But the Republican leader in the Senate, Bill Frist, said attacking the commander-in-chief simply did not make sense. He warned a censure resolution would send the wrong signal around the world.
Earlier this year, two civil liberties groups in the US took legal action to block the domestic spying programme.