AT&T Inc. said it plans to sue the Federal Communications Commission if the agency doesn’t let the company withdraw its application to buy a smaller rival for $39 billion.

The FCC is obligated by its own rules to honor AT&T’s move to rescind its application to acquire T-Mobile USA Inc., Wayne Watts, general counsel for AT&T, said today in a blog entry.

“We have every right to withdraw our merger from the FCC, and the FCC has no right to stop us,” Watts said in the entry on the company’s public policy blog. “Any suggestion the agency might do otherwise would be an abuse of procedure which we would immediately challenge in court.”