US: A top senate Republican has warned the White House that it is heading for a "constitutional confrontation" with congress over surveillance of phone calls made by American citizens.
The warning came as lawyers for the house of representatives described as "both unconstitutional and unnecessary" an FBI search of congressman William Jefferson's office last month.
Senate judiciary committee chairman Arlen Specter accused vice-president Dick Cheney of going behind his back to persuade other Republicans on the committee to oppose a thorough investigation into the National Security Agency's spying on domestic phone calls.
In a letter to Mr Cheney this week, Mr Specter complained that the vice-president had kept him in the dark about his lobbying of other Republicans.
"I was surprised, to say the least, that you sought to influence, really determine, the action of the committee without calling me first, or at least calling me at some point," he said. "This was especially perplexing since we both attended the Republican senators' caucus lunch yesterday and I walked directly in front of you on at least two occasions en route from the buffet to my table."
Mr Specter said that if the White House did not co-operate with the committee, he would work with Democrats to subpoena phone company executives to explain their role in the surveillance programme.
The senator told Mr Cheney that the latest dispute came on the heels of a succession of attempts by the White House to expand its power at the expense of congress.
"There are the presidential signing statements where the president seeks to cherry-pick which parts of the statute he will follow . . . There is the recent executive branch search and seizure of Congressman Jefferson's office," Mr Specter wrote. "There are recent and repeated assertions by the Department of Justice that it has the authority to criminally prosecute newspapers and reporters under highly questionable criminal statutes."
House of representatives general counsel Geraldine Gennett has told a court investigating the legality of the FBI's search of Mr Jefferson's office that the justice department had no right to keep material found there.
"A blatant constitutional violation occurred when the FBI agents executed the warrant on Congressman Jefferson's office," she wrote in a brief to the court.
The FBI says it filmed Mr Jefferson, a Democrat from Louisiana, accepting a bribe and that it found $90,000 in cash hidden in the freezer at his apartment. Last month's raid on Mr Jefferson's office was unprecedented and congressional leaders complain that it violates the separation of powers between the executive and legislative branches.
A few days after the search, President George W Bush responded to the congressional outcry by imposing a 45-day freeze on the examination of the items found in Mr Jefferson's office. He barred anyone from examining them until a judge ruled if the search was lawful.