Of course this must also take a whole count if you want to encourage your partner to do the same. Take your time and aim to close right on the beat. The follower as always must yearn with her upper body toward her partner while gathering her left foot to its counterpart on 5. What sometimes helps in practicing is for the follower not to cross, but simply to close. It's all the same, but the stress is less.
Wisdom is easier said than done, in any case.
However, specific responsibilities of each partner are different. The leader must establish the overall timing, the tempo. Then the woman maintains that tempo for whatever she does - hopefully by listening to the music. That includes the cross, but also everything else. At any time the man can change that timing.