TEHRAN, Iran (AP) — Iran’s supreme leader on Monday signaled support for Tehran’s nuclear negotiations to secure sanctions relief, a rare reference to the still-halted talks as world powers near a diplomatic turning point. Ayatollah Ali Khamenei stressed the importance of Iranian economic self-sufficiency during a lengthy televised speech on the occasion of Nowruz, the Persian New Year. But he quickly added: “I do not say that you should not seek to lift the sanctions. Those who are trying and working in that field, there is no problem.” Khamenei, whose pronouncements are considered vital as h…