At a news conference in Brazil, U.S. Defense Secretary Leon Panetta urged North Korea not to engage in anybr br provocation that could increase instability, as speculation mounts about a possible third nuclear test.br br (SOUNDBITE) (English)U.S. DEFENSE SECRETARY LEON PANETTA, SAYING:br br "I again would strongly urge them not to engage in any kind of provocation - be it nuclear testing or any other act -br br that would provide greater instability in a dangerous part of the world. I do not have any specific information as to whether or notbr br they will proceed or not with additional provocations at this time.