Ratings agency Moody's today said metals and mining major Vedanta Resources' over Rs 19,000 crore impairment in Cairn India is credit negative as it implies a longer pay back period. Last month, Vedanta said in the January-March quarter it wrote off Rs 19,180 crore as non-cash impairment charge for acquisition goodwill of Cairn India following slump in global crude oil prices. "The USD 3.1 billion impairment is credit negative for Vedanta Resources Plc (Vedanta, Ba1 negative), which owns 62.8 per cent of Vedanta Ltd, because it implies a longer payback period for the acquisition and increases the challenge of repaying USD 4.4 billion of acquisition debt financing from its operating cash flow," Moody's said in a statement. Vedanta Ltd owns 59.9 per cent of Cairn India, which it purchased in 2011.