A closure for a container comprises: a pouring spout having a neck defining a pour opening and a cover portion closing one end of the neck; a cap fittable to, and removable from, the pouring spout; a cam for transforming rotation into a stroke having a rotational component and a translational component to couple/detach the cap with/from the pouring spout; a weakening line on the end of the neck; first opening promoting mechanism on the cover portion; and second opening promoting mechanism on the cap to engage the first opening promoting mechanism upon removing the cap from the pouring spout to separate the cover portion from the neck along the weakening line; the first and second opening promoting mechanisms comprise at least one further cam element arranged along an angular portion of the annular periphery of the cover portion to enhance lifting thrust produced by the cap on the cover portion.