  The AMS Collaboration has recently released precision data on cosmic ray (CR)
leptons and protons at high energies. Interesting progresses have also been
made on the measurement of CR nuclei, such as the boron-to-carbon ratio or the
lithium spectrum, up to TeV/nucleon energies. In order to provide a description
these data, I consider a diffusion model of CR propagation which allows for
latitudinal variations of the CR diffusion properties in the Galactic halo. I
discuss the role of high-precision data on light CR nuclei in resolutely
testing this model and the key propagation parameters.
