The Department of Justice has written a letter to the Federal Communications Commission asking it to "defer action" on the agreement Sprint Nextel (NYSE:S) made with mobile operator SoftBank. That deal proposes selling 70% of Sprint to the Japanese company for $20 billion.

The DOJ letter dated Jan. 28 states that it, along with the Federal Bureau of Investigation, and "with the concurrence of the Department of Homeland Security," need more time in which to review the pending buyout for any  "national security, law enforcement, and public safety issues."

The request does not give an expected date for the completion of the law enforcement agencies' review.