Updated: 1:18 p.m.Senate Democrats will continue working their way through Majority Leader Harry Reids (D-Nev.) legislative to-do list this week, hoping to take up a Federal Aviation Administration bill that Reid has defined as part of his jobs agenda. But Senate Republican Conference Chairman Lamar Alexander (Tenn.) and Sen. Bob Corker (R-Tenn.) have refused to agree to begin debate on the measure unless Democrats agree the final bill will not include provisions changing the law under which Federal Express employees are unionized. FedEx is based in Memphis, Tenn.Although the dispute has not yet risen to the level of leadership involvement, staff acknowledged it may be difficult to broker a deal, setting up a potential filibuster by Alexander and Corker.The House-passed version of the FAA measure includes provisions subjecting FedEx employees to trucking company unionization laws, rather than those laws that govern airlines and air freight businesses. FedEx has opposed the House language, which the Senate version does not include. A spokesman for Alexander said the lawmaker would use any means necessary to ensure language changing FedExs status under the nations labor laws is not changed. Sen. Alexander will use every legislative tool available to stop Congress from passing a law that singles out how FedEx is governed under federal labor law, the spokesman said. Although Democrats privately acknowledge casting the FAA bill as a jobs bill is a bit of a stretch, the final version of the bill that goes to President Barack Obama could include significant labor-related language, particularly if the FedEx provisions make it into the final product. Democrats are still looking for a solution that would allow them to begin work on the bill this week. But a GOP filibuster of the legislation could provide them with another chance to try to paint Republicans as obstructionists in the runup to the health care fight.