Sen. Richard Shelby, R-Ala., has placed "holds" against several of President Obama's nominees in an effort to force presidential action on the Air Force refueling tanker and other matters.

A hold means that the Senate cannot vote on the nominee. An aide to Shelby confirmed that the holds had been imposed, but he did not identify the nominees.

Shelby is particularly peeved about the refueling tanker because a tanker contract worth up to $35 billion was awarded to Northrop Grumman and Airbus last year, but later voided in a bid protest filed by Boeing. The Northrop tankers would have been assembled in Mobile, Ala.

In a written statement, Shelby said Air Force efforts to build new tankers have been stalled for nearly 10 years and "we still do not have a transparent and fair acquisition process to move forward."

Shelby said the draft request for proposals — an Air Force document asking companies to submit proposals for building new tankers — "needs to be significantly and substantively changed."

Northrop has said it might not bid for a tanker contract because the RfP appears to favor Boeing.

Shelby also wants Obama to release funds so the FBI can build a Terrorist Explosive Devices Analytical Center in Alabama, the statement said.