San Francisco ? Federal agents continue to eavesdrop on Americans’ electronic communications without warrants a year after President Bush confirmed the practice, and experts say a new Congress’ efforts to limit the program could trigger a constitutional showdown.

High-ranking Democrats set to take control of both chambers are mulling ways to curb the program Bush secretly authorized a month after the Sept. 11 attacks. The White House argues the Constitution gives the president wartime powers to eavesdrop that he wouldn’t have during times of peace.

“As a practical matter, the president can do whatever he wants as long as he has the capacity and executive branch officials to do it,” said Carl Tobias, a legal scholar at the University of Richmond in Virginia.

Lawmakers could impeach or withhold funding, or quash judicial nominations, among other measures.

The president, however, can veto legislation, including a law demanding the National Security Agency obtain warrants before monitoring communications. Such a veto would force Congress to muster a two-thirds vote to override.