A search for the direct production of pairs of charginos, each decaying into a lightest neutralino and a W-boson, which in turn decays leptonically, is presented. Previous LHC Run 2 analyses have already excluded the existence of chargino and neutralino in regions where the difference between their masses is larger than the W-boson mass with a 95% CL. The aim of the current search is to explore the so called ``compressed regions'', with a chargino-neutralino mass difference of the order of the W-boson mass. The analysis strategy uses machine learning techniques to improve the Standard Model background rejection. The analysis targets events with two leptons, missing transverse energy and no hadronic activity in the final state, and uses $pp$ collision data at 13 TeV collected by the ATLAS experiment during Run 2 at LHC, corresponding to an integrated luminosity of 139 fb$^{-1}$.