Turin, September 12 - Italy needs credibility on the international financial markets to be able to pay down its huge public debt, the biggest in the eurozone after Greece's, Premier Enrico Letta said Friday. "To pay our debts we have to be credible because no one will buy our debt if we aren't," Letta said amid uncertainty over his government's future that has driven up borrowing costs. Letta called the public debt "the No. 1 problem of the country, a nightmare that is eating our future as we try to solve today's problems with our children's money". Italy's sovereign debt is around 130% of gross domestic product and has made investors wary since the onset of the euro crisis. Letta's unprecedented left-right government is threatened by a looming showdown between the main partners, his centre-left Democratic Party and ex-premier Silvio Berlusconi's centre-right People of Freedom (PdL) party, over Berlusconi's ejection from the Senate following a tax-fraud conviction.