Pressures by media companies to generate ever-greater profits are threatening the very freedom the nation was built upon, former CBS News anchor Walter Cronkite warned Thursday.

In a keynote address at Columbia University, Cronkite said today's journalists face greater challenges than those from his generation. No longer could journalists count on their employers to provide the necessary resources, he said, "to expose truths that powerful politicians and special interests often did not want exposed."

Instead, he said, "they face rounds and rounds of job cuts and cost cuts that require them to do ever more with ever less."