European Union (EU) leaders are locked in late night crisis talks over treaty change at a crunch summit on the eurozone debt crisis with the aim of saving the single currency.<br /><br />The summit in Brussels was undermined early on Friday by a European Central Bank (ECB) warning that there will be no big boost in rescue funding.<br /><br />Leaders took tentative steps to implement a so-called "golden rule" asking countries to set balanced budgets until debt levels drop, although this was only agreed "in principle" with political wriggle room remaining, diplomats said.
