The Senate minority leader, Harry Reid, Democrat of Nevada, broke off talks on Monday with his Republican counterpart on efforts to head off a showdown on judicial nominations, saying he could not consent to Republican demands.

"The negotiations are over," Mr. Reid said as he left the office of the majority leader, Senator Bill Frist of Tennessee. "I have tried to compromise, and they want all or nothing, and I can't do that. It will have to be decided on the Senate floor, hopefully this week."