The Washington Post is reporting that two of Barack Obama’s nominations to fill top science posts have been put on hold by Robert Menendez, a Democratic senator from New Jersey.

Both John Holdren, nominated to lead the Office of Science and Technology Policy, and Jane Lubchenco, for the National Oceanic and Atmospheric Administration, were endorsed last month by the Senate commerce, science and transportation committee after their relatively tranquil nomination hearing (see Nature coverage here). The full Senate must now vote on their nominations, but any senator can place a hold on an action for any reason. To break the stalemate, Menendez must either drop the hold or Senate leaders must force a vote to break the hold that would require 60 votes to pass.

According to the Post, “Menendez is using the holds as leverage to get Senate leaders’ attention for a matter related to Cuba rather than questioning the nominees’ credentials.” Menendez, who is of Cuban descent, has criticized the Castro rule in Cuba.