WASHINGTON - The White House nominee to become the senior U.S. diplomat to Latin America has hit a bump on the road to Senate approval.A Democratic senator, Max Baucus of Montana, has put a ''hold'' on the nomination of Roger F. Noriega to serve as assistant secretary of state for the Western Hemisphere.A Baucus spokeswoman said the legislative move blocking further action has nothing to do with Noriega's qualifications. Rather, Baucus is using the ''hold'' on Noriega to pressure Senate Majority Leader Bill Frist to allow an up-or-down vote on the full Senate floor for his proposal to relax U.S....