A demonstrator holds a newspaper with the headline "Black day for the press" during a protest outside the Cumhuriyet newspaper headquarters in Istanbul, Turkey, November 27, 2015. REUTERS/Osman Orsal

WASHINGTON (Reuters) - U.S. President Barack Obama on Friday said he was troubled by trends in Turkey against a free press and said he had urged President Tayyip Erdogan not to pursue a strategy of repression and shutting down democratic debate in his country.

Obama, speaking to reporters at the conclusion of a nuclear security summit, said Turkey’s cooperation with the United States had been critical on a number of international issues despite disagreements between the two countries.

Two high-profile journalists are on trial in Turkey for publishing footage that purportedly showed Turkey’s intelligence agency shipping truckloads of weapons to opposition fighters in Syria in early 2014.

Erdogan has said he will continue to sue anyone who insults him in Turkey, where journalists and critics of the president have been put in prison.

“I think the approach that they’ve been taking towards the press is one that could lead Turkey down a path that would be very troubling,” Obama said.

“(Erdogan) came into office with a promise of democracy, and Turkey has historically been a country in which deep Islamic faith has lived side by side with modernity and an increasing openness. And that’s the legacy that he should pursue, rather than a strategy that involves repression of information and shutting down democratic debate.”