TALLINN (Reuters) - The European Union should add more sanctions on North Korea as part of international pressure following Pyongyang s largest nuclear test to date, the bloc s foreign policy chief Federica Mogherini said on Thursday. While sanctions have so far done little to stop North Korea boosting its nuclear and missile capacity, Federica Mogherini said more such steps were required along with piling on political pressure.  I would propose to ministers today to strengthen the economic pressure on North Korea, supporting a new U.N. Security Council resolution adopting tougher economic measures, starting new autonomous EU sanctions... and working with other partners in the world to make sure that everybody implements fully and strictly the already-decided economic measures,  Mogherini told reporters before meeting the EU defense and foreign ministers in the Estonian capital. The United States and China are discussing options to rein in Pyongyang and South Korea has deployed a defense system aimed at countering North Korean missile attacks. No formal EU decision is expected from the bloc on Thursday and its leverage on Pyongyang, as well as Russia and China   North Korea s main ally   is limited.   It has to be pursued because the alternative in our view is and could be extremely dangerous, especially if in front of you have an interlocutor that might act quite irrationally.  