Italy's Prime Minister Silvio Berlusconi released a statement on Monday expressing disagreement with his ally Umberto Bossi, after the Northern League leader questioned Italy's future as a unified country. In a rare statement taking issue with his powerful coalition ally's comments, Berlusconi said: "I am sorry, this time, to not agree with my friend Umberto Bossi. I am deeply convinced that Italy will always exist." Earlier, Bossi said the unified Italian system was destined to end and called for independence for the north of the country, which the pro-devolution League says subsidises the poorer south. The mercurial League leader often sparks controversy with comments on issues such as immigration and corruption in the south, but it is unusual for Berlusconi to make a point of publicly disagreeing with him. The discord comes at a time of heightened tension in the centre-right coalition over the content of a 45.5 billion-euro austerity package aimed at balancing the budget by 2013, which started its passage through parliament on Monday. Proposals from Berlusconi's PDL party to reform pensions have been fiercely opposed by the Northern League, on whom Berlusconi depends for his majority in parliament. A plan by PDL secretary Angelino Alfano to raise the retirement age was described as "useless" by League member Roberto Calderoli, who told daily La Stampa on Monday that "pensions can't be touched". The austerity decree must be passed by mid-October, or 60 days after its presentation by the cabinet. However, Italy is under pressure from financial markets and its international partners to approve the package considerably earlier.