WASHINGTON (Reuters) - The head of the International Monetary Fund (IMF) on Friday pressed Europe to provide "significant" debt relief for Greece, saying Athens could not put its fiscal house in order on its own. In a statement issued as euro zone finance ministers wrapped up six hours of talks on Greece, IMF Managing Director Christine Lagarde said it was "critical for medium and long-term debt sustainability that Greece's European partners make concrete commitments ... to provide significant debt relief, well beyond what has been considered so far. ...