Large volumes of Internet traffic are nowadays generated by BitTorrent. In this article, we propose the insertion of high-bandwidth ISP-owned peers as an optimization approach to improve end-users' performance and reduce inter-domain traffic. An ISP-owned peer participates in BitTorrent swarms in order to download chunks and subsequently serve regular peers. We have run simulations on the ns-2 platform showing that our approach results in considerable reduction of both inter-domain traffic and the downloading times of users. We also show that the insertion of an ISP-owned peer can complement effectively the use of locality awareness, and lead to further performance improvements.