The top Republican on the Senate Judiciary Committee warned Monday that he would seek to slow Supreme Court nominee Elena Kagan's path to confirmation unless senators get full access to her files as a Clinton administration aide.

"We're heading to what could be a train wreck," Sen. Jeff Sessions of Alabama said. "I don't believe that this committee can go forward with an adequate hearing" without all records from Ms. Kagan's tenure as a White House counsel and then domestic policy adviser to President Clinton.

Sen. Patrick J. Leahy, Vermont Democrat, the Judiciary Committee chairman, last week set hearings to begin on June 28. Mr. Sessions said Republicans would ask for a delay unless senators get access to the tens of thousands of pages of Clinton-era records by then...