International Monetary Fund chief Christine Lagarde has warned the US it has the potential to be its "own worst enemy” over the fragile economic recovery and that failure to reach a comprehensive settlement over the fiscal cliff could see growth plummet to zero.In forthright comments over the impending fiscal cliff, the IMF managing director said that "if the US economy was to suffer the downside risk of not reaching a comprehensive deal, then growth would be zero”. The markets would react quickly, "and the stock market would take a hit,” she said.All the current signs of optimism over the economy that she identified – including falling unemployment, the housing sector bottoming out and reduced household debt – would be negated.Speaking on CNN’s State of the Nation, Lagarde predicted that the diverse landscape of the US economy "could be significantly improved or worsened by the fiscal cliff, fiscal deficit and the debt of the country that are three topics that can be addressed now in a comprehensive fashion.” She added: "The real threat is here, with us, and that can be addressed.”The cautionary words of the IMF chief underlined how closely the world is watching the fast-approaching fiscal cliff deadline. On 1 January, if Congress does not act, a package of $600bn spending cuts and tax rises will automatically kick in, sending shock waves around the world that could damage what she characterized as the slow and laborious economic improvements being made across the Eurozone.But the message Lagarde was clearly hoping to deliver was that failure to reach a comprehensive deal on all three factors – the fiscal cliff, debt ceiling and long-term debt – would hurt the US far more than it would hurt anyone else. The US she said "is more exposed to its own difficulties and issues than elsewhere in the world because it is such a big player. Agencies