WARSAW (Reuters) - Poland's broadcasting regulator on Wednesday extended an operating license for the popular U.S.-owned, anti-government news channel TVN24, which critics say is a prime target in ruling party efforts to quash media freedom.

       The license of TVN24, which is Poland's most popular news channel, was set to expire on Sept. 26. Its fate was uncertain after the lower house of parliament passed a bill last month to strengthen a ban on firms from outside the European Economic Area controlling Polish broadcasters.

       TVN, the parent company of TVN24, has been owned by U.S. entities since 2015 via a firm registered in the European Union to adhere to the requirements of the ban on non-European firms owning more than 49% of Polish media.

       Although the regulator extended the license on Wednesday, it also passed a resolution to ask the government for clearer legislation on the ownership question as well as legal clarification from the Constitutional Tribunal.

       Poland's ruling Law and Justice (PiS) party, which is fighting to retain its majority in the lower house, has long argued that foreign-owned media distort public debate and do not serve Polish interests. Critics say the government only wants to control the media and curb free speech.

       Since the party took office in 2015, Poland has dropped to 64th place from 18th on the World Media Freedom Index.

       The opposition-led upper house of parliament rejected the media bill, but the leader of PiS signalled the party will try to overturn the rejection before the end of September.

       (Reporting by Joanna Plucinska and Alicja Ptak; Editing by Chris Reese and Sonya Hepinstall)