BEIRUT, Lebanon — After trying for months to engage with Syria in an effort to ease the violence there, Turkey’s president declared Sunday that he had “lost confidence” in the government in Damascus, and he stopped just short of calling on President Bashar al-Assad to step down.

“Clearly we have reached a point where anything would be too little too late,” the Turkish president, Abdullah Gul, told his country’s Anatolia news agency, expressing frustration that Mr. Assad’s violent crackdown on protesters has continued past the 15-day window in which Turkey had said it expected a change.

“Today in the world there is no place for authoritarian administrations, one-party rule, closed regimes,” Mr. Gul said, adding that such governments could be “replaced by force” if their leaders did not make changes.

“Everyone should know that we are with the Syrian people,” he said.

The statements were particularly harsh coming from Turkey, which has invested enormous diplomatic efforts in Syria in recent years and has struggled to mediate the current crisis. Mr. Gul’s remarks also sharply increased pressure on Mr. Assad on a day when his Interior Ministry urged the residents of Damascus to stay home “for their own safety” and not to respond to online calls for protests in the capital.