Even at 1-2 years, though, screen time remains anathema.
1-2 year old kids should be spending at least three hours each day engaged in physical activities, too.
"Achieving health for all means doing what is best for health right from the beginning of people's lives", Ghebreyesus said.
Childhood is the time when children have fun exploring the neighbourhood, and not be glued to their gadgets!
Tim Smith, Reader in Cognitive Psychology, Centre for Brain and Cognitive Development, Birkbeck, University of London, said: "In recent months United Kingdom parents of 0- to five-year-olds and early-years practitioners have been bombarded with conflicting recommendations and guidelines about how and whether they should be managing their children's screen time and sedentary behaviour, e.g. from the RCPCH and Chief Medical Officers".
Shorter sleep duration has been associated with more TV viewing and time spent playing computer games, it added.
Several experts noted, however, that WHO's broad recommendations were based on thin evidence.
Instead, "when sedentary, engaging in reading and storytelling with a caregiver is encouraged", the organisation said of young children.
The WHO guidance, created to help national policymakers, also includes advice on physical activity, and sleep among under fives.
"Improving the physical activity, sedentary and sleep time behaviors of young children will contribute to their physical health, reduce the risk of developing obesity in childhood and the associated non-communicable diseases in later life and improve mental health and well-being", the WHO said.
Stephen Balkam, founder and chief executive of the Family Online Safety Institute, whose members include such technology industry players as Google, Facebook and Amazon, said there's an important difference between "screen time" and "screen use". Children aged one to two years old should spend at least 180 minutes being active and 11 to 14 hours sleeping, the report states. "What we really need to do is bring back play for children".
"Our research has shown that now there is not strong enough evidence to support the setting of screen time limits", said Dr. Max Davie, the college's Officer for Health Improvement.
Concerns about screen time begin well before children start reaching for their parents' iPads and smartphones, said Emily Oster, a professor of economics at Brown University and the author of "Cribsheet: a Data-Driven Guide to Better, More Relaxed Parenting". "Make sleep and physical activity a priority", she said.
The new guidelines are "straightforward" and "give parents some parameters to follow when it comes to sleep, physical activity and limiting screen time", said Dr. Jennifer Shu, an Atlanta-based pediatrician and spokeswoman for the American Academy of Pediatrics, who was not involved in the World Health Organization guidelines. "These ideas that kids are going to be physically active and get enough sleep - that's a good idea, but it's not all about screens".