Crossing branches can be removed when they are seen.

Do it now. Your tree has plenty of other leaves to take over.

Thanks for the quick response, however I failed to mention that the tree was planted in March 2013 zone 7 & hasn't established itself yet. Should I wait 2 growing seasons before cutting on it. There are so many conflicting care instructions given online, that I don't know the exact season to prune. Is it in the late Fall or early Spring for zone 7? Online says Jan., but wouldn't it be exposed to frost & be at risk?! Please help. Thank you

"...the tree was planted in March 2013 zone 7 & hasn't established itself yet. Should I wait 2 growing seasons before cutting on it."

If you were "limbing-up" for aesthetic reasons, I'd say sure, wait until the second growing seasons to give your crape time to get established. However, in the case of diseased, dead, or rubbing branches, you can go ahead and prune them at your earliest convenience.

"...I don't know the exact season to prune. Is it in the late Fall or early Spring for zone 7?"

The ideal time for pruning crapes is late winter to very early spring. Pruning during this time will ensure that the plant is able to cover over the wounds as quickly as possible. It's also a good time because there are no leaves and you can more easily tell what you are doing. All this doesn't mean you couldn't prune at some other time. I would avoid pruning really late in the growing season, which would encourage new growth that wouldn't have time to harden off before winter.