By James Mackenzie
ROME (Reuters) - Italy marked 150 years as a unified state on Thursday, inviting world leaders to festivities that contrasted starkly with a febrile political mood after crushing local election losses for Prime Minister Silvio Berlusconi.
Russian President Dmitry Medvedev, U.S. Vice President Joe Biden, China's Vice President Xi Jinping and Argentinian President Cristina Fernandez have all paid calls on Italian head of state Giorgio Napolitano.
The center of Rome was locked down for a military parade watched by the leaders and dozens of others including representatives from countries with large Italian emigrant populations like Australia or Canada.
Unification celebrations have been going on in Italy all year, although enthusiasm has been muted in a country where regional attachments have traditionally provided a much more powerful sense of identity than the nation.
Berlusconi's various legal problems, from corruption charges to accusations of paying for sex with an underage prostitute, have also helped fuel a particularly toxic political climate that has outweighed any sense of national unity.
Thursday's parade near the Colosseum featured armored cavalry from the president's ceremonial guard, units back from service in Afghanistan and feather-capped Bersaglieri trumpeters loping past in their traditional running march.
But this week's devastating local election losses for the prime minister's center-right coalition has overshadowed the celebrations.
Defeats in cities across the country from the financial capital Milan to the southern port of Naples have cast a deep gloom over the government and aroused hopes in the opposition that the Berlusconi era may finally be nearing its end.
The 74 year-old prime minister's appearance at the parade was greeted by the usual mix of applause from supporters and derisive whistles from opponents but even in his own camp, worries about his future have grown.
The Northern League, the pro-devolution coalition party whose seats in parliament are vital for the government, has been particularly nervous, fearing that its solid regional base may be eroded by its association with the scandal-hit premier.
Berlusconi has pledged to carry on until the next parliamentary elections in 2013 but the uncertainty has raised doubts about the government's ability to carry out reforms of Italy's stagnant economy, one of the most sluggish in Europe.
A referendum on June 12-13 to decide on whether to relaunch the nuclear power sector is likely to provide the next concrete test of the government's popularity, with voters expected to reject the plan overwhelmingly.
Fearing a heavy loss in the wake of the Fukushima disaster in Japan, the government had hoped to avoid the referendum but was forced to go ahead with the vote after a ruling by Italy's highest court on Wednesday.
(Editing by Jon Boyle)