WASHINGTON -- A group of Republican senators led by David Vitter of Louisiana sent a letter to Senate Majority Leader Harry Reid (D-Nev.) Thursday that they will block any legislation that does not make cuts to government to reduce the national debt. If they follow through on a pledge to filibuster, the GOP group could effectively derail Senate action until the chamber reaches a compromise with the House over budget cuts, which could take weeks or longer. "We're telling Sen.