BY TIM JOHNSON

  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. restrictions on travel to Cuba.

  Observers said the tactic might delay a Senate vote on Noriega's nomination into June but probably not imperil it.

  Nonetheless, the Baucus move marked the kind of political maneuvering that has left the key State Department post on Latin America without a

  Senate-approved nominee for more than four years. Since late 1998, the post has been filled on an interim or appointed basis.

  Noriega, the current U.S. ambassador to the Organization of American States, sailed quietly through a hearing of the Senate Foreign Relations Committee early this month. Supporters expected him to get a floor vote of approval in the Senate by the end of May.

  But now that won't happen. The thorny issue of sanctions on Cuba has come in the way.

  On April 30, Baucus and a Republican senator, Michael Enzi of Wyoming, jointly helped introduce a bill to lift restrictions that bar most U.S. citizens from traveling to Cuba.

  While the bill now has 16 co-sponsors, the White House has made clear it has no intention of relaxing any aspect of the four-decade-old trade embargo against the regime of Fidel Castro, who is the longest ruling communist leader in the world.

  The issue of sanctions on Cuba has become a peculiar domestic policy lodestone. President Bush, eager to win re-election in 2004, seeks support in the linchpin state of Florida with a hard line toward Castro. Meanwhile on Capitol Hill, bipartisan groups of legislators in both chambers say they have the votes to weaken the embargo but have been thwarted by the White House in getting such legislation passed and enacted.

  A spokeswoman for Baucus, Laura Hayes, said the senator has no intention of harming Noriega's chances of approval.

  ''The hold has nothing to do with Noriega,'' Hayes said. ``If Sen. Frist agrees to a vote on Monday [on the Cuba travel bill], then the hold is all gone.''