Prospects for the first Top pair cross section measurement in the semileptonic and dilepton channels at CMS

Although the top quark has been discovered in 1995 and studied extensively by the Tevatron experiments, the top quark will remain special for years to come due to unique opportunities it offers. Because of the large top-antitop production cross section and high luminosity, the LHC would be a Top factory, producing a large sample of top quarks even at the initial low luminosities. This will enable a rich program of top quark physics to be explored, both within the Standard Model and using top quarks as probes of physics beyond the Standard Model. Prospects for the observation of top pair production in the proton-proton collisions at the center of mass energy $\sqrt{s}$=10 TeV in the dilepton and lepton+jets final state are discussed. The emphasis is put on analysis strategies for the early phase of CMS operation with data corresponding to integrated luminosities of 10-20 pb$^{-1}$ considering a realistic detector performance.