Two-loop large Higgs mass correction to the rho-parameter

The two-loop correction to the rho-parameter in the limit of the large Higgs mass is calculated. Numerically it is found that the two-loop contribution is equal in magnitude, but of opposite sign to the one-loop correction if the Higgs mass is about 137 times the vector boson mass. The calculation suggest a breakdown of perturbation theory if the Higgs mass is larger than 3 TeV. There is not direct correspondence between our results and the poles at n=3 of the simple non-linear sigma-model at the two-loop level. (orig.)