U.S. Senate Republican leaders insist that spy agencies continue to have access to data on Americans' telephone calls despite a court ruling that the practice is illegal, but aides said on Friday they may have to compromise on proposed reforms of the program before it expires on June 1.

Senate aides said the deadline could force supporters and opponents of the bulk data collection program to work out a deal before May ends. In practice the date may be even earlier as Congress leaves Washington on May 22 for a Memorial Day recess.

Sen. Mitch McConnell, the Republican Majority Leader, and Richard Burr, chairman of the Senate Intelligence Committee, defended the data collection shortly after a federal appeals court three-judge panel in New York ruled the practice illegal on Thursday.