[en] The equilibrium properties of a system of particles whose interaction is described by the Yukawa potential are studied. Liquids and crystals with bcc and fcc lattices near the melting line are considered. The latent heat of melting for crystals and the density change during the phase transition are calculated. We analyze the temperature dependences of the thermodynamic quantities near the melting line and calculate the thermal expansion coefficient and the heat capacity at constant pressure. We show that the state of a Yukawa system cannot be uniquely defined by a pair of dimensionless quantities, the temperature and the pressure, which use the interaction potential parameters (the product of the charges and the screening length) as scales. In particular, the position of the melting line is ambiguously determined on a two-parameter phase diagram constructed in dimensionless quantities.