The Mn spin correlations were studied near the O -O phase transition at TJT = 750 K, up to 950 K with 17 O and 139 La NMR in a stoichiometric LaMnO3 crystalline sample. The measured local hyperfine fields originate from the electron density transfered from the e g -and t 2g -orbitals to the 2s(O) and 6s(La) orbits, respectively. By probing the oxygen nuclei, we show that the correlations of the Mn spins are ferromagnetic in the ab-plane and robust up to TJT whereas along the c-axis, they are antiferromagnetic and start to melt below TJT , at about 550 K. Above TJT the ferromagnetic Mn-Mn exchange interaction is found isotropic. The room temperature orbital mixing angle, ϕnmr = 109 ± 1.5• , of the e g ground state is close to the reported value which was deduced from structural data on Jahn-Teller distorted MnO6 octahedra. For T > TJT LaMnO3 can be described in terms of non-polarized eg-orbitals since both eg-orbitals are equally occupied.