^Condition to start relative motion

Suppose a body A at rest over another body B. Let the limiting friction acing between them is f_LAB. If a net force F acts on A which tends to start motion of A relative to B then the condition to start motion of A relative to B is F > f_LAB. If F > f_LAB then A will remain at rest relative to B. However if

F > f_LAB then  A accelerates relative to B & a kinetic friction between A & B acts.