Systems and methods for allocating transmit power among multiple interfaces in a wireless communication system are disclosed. In one embodiment, the method comprises determining a first power level that is used for transmitting over a first air interface, determining a maximum power level available for transmitting over a second interface, comparing the first power level to the maximum power level, determining a second power level that is used for transmitting over the second air interface based on the comparison of the first power level to the maximum power level, and generating a power-based payload constraint based on the second power level.