The United States on Tuesday moved to add more pressure on Libyan leader Muammar Gaddafi by imposing sanctions on more Libyan entities while lifting sanctions against a senior government official who broke with the leader.

In a series of actions, the Department of Treasury's Office of Foreign Assets Control (OFAC) identified three foreign Libyan- owned banks and six additional companies subject to sanctions, and lifted sanctions against former Oil Minister Shukri Mohammed Ghanem, who defected last month.

The Treasury accused the three banks -- Arab Turkish Bank, a joint-venture between Arab and Turkish shareholders; the Tunisia- based North Africa International Bank, and the North Africa Commercial Bank based in Lebanon -- of involvement in commercial transactions with their parent bank -- the Libyan Arab Foreign Bank, already put under sanction.

The department identified six additional companies owned by the Libyan government as being subject to sanctions along with the three banks. The companies are General Company for Chemical Industries, General National Maritime Transport Company, Ghana Libya Arab Holding Company and its subsidiary Glahco Hotels And Tourism Development Company Limited (Golden Tulip Accra), Libyan Norwegian Fertilizer Company and Pak-Libya Holding Company.

"The Treasury Department is carefully monitoring Libyan-associated entities worldwide to ensure that they are not attempting to evade sanctions and assist the Gaddafi regime," OFAC Director Adam Szubin said. "We will remain vigilant in our efforts to isolate the Gaddafi regime from the international financial system."

In another move, the Treasury lifted sanctions against Ghanem, who was also chairman of the National Oil Corporation of Libya but defected in May 2011.

"Our sanctions are intended to prevent harm and change behavior, " Szubin said. "To the extent that sanctioned individuals distance themselves from the Gaddafi regime, these measures can be lifted."

The U.S. started to slapped sanctions on senior Libyan government officials and entities in late February, and froze some 34 billion U.S. dollars of Libyan government assets.

The NATO-led alliance is stepping up its air raids on Libyan government targets, which started on March 19. U.S. President Barack Obama has been criticized at home for sending U.S. forces into "hostilities" without obtaining congressional authorization. But he declared last week that the Libyan campaign should not be considered "hostilities," because U.S. forces are playing a largely supportive and logistical role.

The United States handed over control of the Libyan mission to NATO in late March.