A method of controlling a power transmitter includes entering a negation phase with a power receiver including receiving a foreign object detection status packet from the power receiver, detecting whether a foreign object is present based on the foreign object detection status packet, and transmitting a NACK response to the power receiver indicating the power transmitter has detected the foreign object is present or transmitting an ACK response to the power receiver indicating the power transmitter has detected the foreign object is not present; and entering a power transfer phase including transmitting a first power to the power receiver in response to the transmitted NACK response and again detecting whether the foreign object is present while transmitting the first power, and transmitting a second power greater than the first power in response to the transmitted ACK response.