Allergan CEO Brent Saunders told CNBC on Wednesday the U.S. government had targeted his company's failed $160 billion deal with Pfizer.



"It really looked like they did a very fine job of constructing a rule here — a temporary rule — to stop this deal, and obviously it was successful," he told CNBC's "Squawk on the Street."



Saunders was referring to new regulations issued Monday by the U.S. Treasury that will prevent so-called inversion deals — under which a U.S. company moves its base to a country with a more favorable taxation environment. The regulation removed the tax benefits New York-based Pfizer had hoped to gain from the deal with Ireland's Allergan.



Saunders singled out the provision in the rules that imposes a three-year limit on foreign companies bulking up on U.S. assets to avoid ownership requirements for a later inversions deal. He said that ban in particular was designed to block the Pfizer-Allergan deal.



Allergan had been blindsided by Treasury's announcement, Saunders said.

"For the rules to be changed after the game has started to be played is a bit un-American, but that's the situation we're in," he said.



"We built this deal around the law, the regulations, all the notices that were put out by the Treasury and it was a highly legal construct," he added. "We followed the rules that Congress had set for companies looking to move to foreign domicile."