Interference minimization problem in wireless sensor and ad-hoc networks is considered. That is to assign a transmission power to each node of a network such that the network is connected and at the same time the maximum of accumulated signal straight on network nodes is minimum. Previous works on interference minimization in wireless networks mainly consider the disk graph model of network. For disk graph model two approximation algorithms with $O(\sqrt{n})$ and $O((opt\ln{n})^{2})$ upper bounds of maximum interference are known, where $n$ is the number of nodes and $opt$ is the minimal interference of a given network. In current work we consider more general interference model, the physical interference model, where sender nodes' signal straight on a given node is a function of a sender/receiver node pair and sender nodes' transmission power. For this model we give a polynomial time approximation algorithm which finds a connected network with at most $O((opt\ln{n})^{2}/β)$ interference, where $β\geq 1$ is the minimum signal straight necessary on receiver node for successfully receiving a message.