The present work developed a new variational line tension model (LTM) that accounts for contributions from the local line energy, long-range interaction among dislocation segments, and interplay between dissociated partials. This new LTM has been shown to accurately predict cross-slip energy barriers under different stress states, verified through atomistic simulations on the face-centered cubic (FCC) nickel model system. We demonstrated that the line tension in general is not a constant, but varies with the local dislocation length and the separation distance between dissociated dislocations, and thus the constant line tension assumption is inherently inadequate. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.