Senate confirmation of two of President Obama's science appointees —John Holdren to lead the White House Office of Science and Technology Policy, and Jane Lubchenco to head the National Oceanic and Atmospheric Administration (NOAA) — is on hold because of political maneuvering on an unrelated issue.

The delay isn’t about the scientists' credentials, but is being used by Sen. Robert Menendez (D–N.J.) as a bargaining chip to gain his colleagues' support on a matter related to Cuba, according to The Washington Post, citing an unidentified source. It's not clear from the story what that matter is, but as the Nature blog The Great Beyond notes, Menendez has previously criticized the Castro regime. Menendez, who is Cuban-Americans, also opposes Senate legislation that would ease travel restrictions to the island nation.

The full Senate must vote on the nominees, and any senator can place a hold on the votes. If Menendez doesn’t drop his objection, Senate leaders could force a vote to break the hold. Both have already been through confirmation hearings. Holdren, a 64-year-old physicist, has pushed for aggressive action to stop global warming, and marine biologist Lubchenco, 61, has criticized NOAA for not doing enough to prevent overfishing. Holdren is on leave from Harvard's Kennedy School of Government, where he most recently was director of the program on science, technology, and public policy. Lubchenco is a professor of marine biology and zoology at Oregon State University.

"We don’t comment on anonymous holds," Menendez spokesman Afshin Mohamadi told

Environmentalists who back Holdren and Lubchenco are annoyed by the delay as Washington gears up for climate talks this week with international dignitaries. Yvo de Boer, the executive secretary of the United Nations Framework Convention on Climate Change, as well as the Danish and Polish climate ministers, are visiting lawmakers to discuss global warming.

"Climate change damages our oceans more every day we fail to act," Michael Hirshfield, chief scientist for the advocacy group Oceana, told the Post. "We need these two supremely qualified individuals on the job yesterday."

Image of Sen. Robert Menendez/U.S. Senate via Wikimedia Commons