KATHMANDU (Reuters) - Nepal's warring political parties failed to meet a midnight deadline to agree on a new constitution on Sunday, plunging the Himalayan republic into further uncertainty, but the government moved quickly to defuse the crisis with a call for elections. A new constitution was widely seen as crucial to ending the instability that has plagued Nepal since the end of a Maoist-led civil war in 2006 and subsequent overthrow of the monarchy, but it has been thwarted by demands for the country to be divided into states along ethnic lines. ...