The catalytic partial oxidation (CPO) of methane/oxygen mixtures with large exhaust gas dilution has attracted increased attention in gas-turbines of new power generation cycles that aim at reduced NO_x and CO₂ emissions. In the present work, ignition and extinction of fuel-rich methane/oxygen mixtures diluted with H₂O and CO₂ is investigated experimentally and numerically at 5 bar. Catalytic ignition (light-off) was well-reproduced by the numerical model. The chemical impact of H₂O dilution, although important during the time evolution of the light-off event, was shown to be minimal on the catalytic ignition delay times. A large hysterisis in the ignition/extinction curve was observed, allowing for stable reactor operation at temperatures as low as 470K.