WARSAW, Poland (AP) — Two of Poland's most famous foes, former President Lech Walesa, and the country's de facto leader, Jaroslaw Kaczynski, faced off in court Thursday, exchanging wry comments.

Kaczynski, the powerful head of the ruling Law and Justice party, is suing Walesa for blaming him in social media posts for the 2010 plane crash in Smolensk, Russia, that killed Kaczynski's twin, then-President Lech Kaczynski, along with 95 others that included top Polish political and military leaders.

In one 2016 post, Walesa alleged that Kaczynski, "guided by bravado," was on the phone pushing for the plane to land in heavy fog.

Kaczynski wants Walesa to admit his words were untrue and that he be forced to pay 30,000 zlotys ($8,000) to charity.

This is the latest in the long history of feuding between Walesa, the founder of the 1980s Solidarity pro-democracy movement that peacefully ended communism in Poland, and Kaczynski, his former ally and aide.

Kaczynski and his twin, who was a top Solidarity activist, promoted Walesa to be democratic Poland's first popularly chosen president in 1990. They became his closest aides, but soon bitterly fell out with him in still unclear circumstances. Walesa has claimed that the brothers wanted control over him.

The Kaczynskis alleged he had been a communist collaborator codenamed "Bolek," which Walesa denies and says documents suggesting that were forged.

Kaczynski still insists that Poland's transformation to democracy was imperfect and left a lot of political and financial influence in the hands of the former communist rulers.

Outside the courtroom in Walesa's hometown, the Baltic port city of Gdansk, the former allies-turned foes sparred verbally Thursday, calling each other "my mistake."

"Why did I ever make you my minister?" Walesa asked Kaczynski as they stood together before entering the courtroom.

"Why did I ever make you the president?" Kaczynski retorted, though both could be seen smiling.

Despite the court's encouragement, they failed to reach an agreement, so more court sessions will be held.