MOSCOW (AP) — Dragging much of Europe into his fight with Ukraine, Russian President Vladimir Putin urged European leaders Thursday to quickly help Ukraine settle its gas debt to Russia to prevent an imminent shutdown of Russian natural gas supplies to the continent. Putin’s letter to 18 leaders, released Thursday by the Kremlin, is part of Russia’s efforts to retain control over its struggling neighbor, which is teetering on the verge of financial ruin and is facing a pro-Russian separatist mutiny in the east.