In this paper, we study power control to minimize packet loss for delay-bounded transmission of bursty sources over Gaussian channels and transmission of constant rate sources over time-varying block fading channels. In the above two problems, we consider the effect of queuing delay on the achievable packet loss rates. First, we show that small additional delay helps substantially reduce the packet loss probability in fading channels. Next, we show that for transmission of bursty sources over Gaussian channels, a small additional queuing delay also leads to reduction in packet loss probability. Finally, the duality between the two solutions is highlighted for a specific delay case, suggesting that the duality holds for all delays. A special case of our results is the traditional channel based power control, which typically assumes that each packet is served as soon as it arrives without any queuing delay.