A high-power optically pumped semiconductor laser operating around 970 nm has been used as a pumping source for an upconversion laser based on an Er3+ doped LiLuF4 crystal. Nearly 0.5 W of continuous wave (cw) output power and 0.8 W peak power at a 50% pump duty cycle could be achieved at a wavelength of 552 nm. This represents the highest output power from a room temperature upconversion laser ever reported. Laser threshold and slope efficiency were measured to be below 100 mW of absorbed pump power and 30%, respectively. This experiment could be an important step along the route to realizing a compact and efficient upconversion laser emitting in the Watt level power regime.