U.S. President Barack Obama expressed concern Friday about the state of democracy in Poland, publicly rebuking a right-wing government that has paralyzed the constitutional court and taken steps to control state run media.

Obama said he shared his worries with Polish President Andrzej Duda in a one-on-one meeting before the opening of a NATO summit in Warsaw.

"I expressed to President Duda our concerns about certain actions and the impasse around Poland's constitutional tribunal," Obama told reporters. "I insisted that we are very respectful of Poland's sovereignty and I recognized that parliament is working on legislation to take important steps but more needs to be done."

Poland has been stuck for months in controversy over the 15-member Constitutional Tribunal, a body that rules on the constitutionality of legislation, playing a role similar to that of the U.S. Supreme Court. The dispute concerns both appointments to the court and the rules that govern how it functions.

Opponents say the government's actions undermine democracy and have held several large street protests in recent months. The government's leaders say it is only trying to correct an imbalance, with appointments by the previous centrist government dominating the court.