In this paper we propose a new method for calculation of the dispersion energy, based on Longuet-Higgins formula, which employs time-independent coupled-cluster response function introduced by Moszynski et al. In contrast to Ref., the integral over the imaginary frequencies is performed analytically, and as the final result we obtain the expression for the dispersion energy in terms of cluster amplitudes, and the so-called dispersion amplitudes which include excitations on both monomers simultaneously and they are the solutions of simple linear equation. The method introduced here is valid for arbitrary truncation of cluster operator, and since the dispersion is expressed only by commutators, the equation is explicitly connected. This opens an avenue for formulation of high-accuracy dispersion energy based on wavefunction methods. In present paper we perform the Moller-Plessett order-by-order perturbation analysis in terms of intramonomer correlation operators W . We introduce a simplified scheme which allows us to calculate the dispersion energy accurate up to the second-order of W operator. We demonstrate how the simplified method works for several small van der Waals systems and compare it with existing methods.