We combine six measurements of the inclusive top-quark pair (t(sic))
production cross section (sigma(t)(sic)) from data collected with the
CDF and D0 detectors at the Fermilab Tevatron with proton-antiproton
collisions at root s = 1.96 TeV. The data correspond to integrated
luminosities of up to 8.8 fb(-1). We obtain a value of sigma tt = 7.60
+/- 0.41 pb for a top-quark mass of m(t) = 172.5 GeV. The contributions
to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from
systematic sources, and 0.21 pb from the uncertainty on the integrated
luminosity. The result is in good agreement with the standard model
expectation of 7.35(-0.33)(+0.28) pb at next-to-next-to-leading order
and next-to-next-to leading logarithms in perturbative QCD