Is it ok to let 3 weeks old infant to sleep on tummy? If so, what is the maximum time allowed for infant to sleep on tummy?

I think tummy is can only if supervised and have to ensure that the surface baby's is sleeping on is solid and woun have much danger if baby face down. We didn't try tummy much and it wasn't my boy's favorite. My boy sleep on his side abt 3/4 the way. I think sleeping tummy only can when much later like 3 months plus when baby can have good neck strength and lift and adjust head well