Luxembourg PM Jean-Claude Juncker has resigned after losing parliamentary support over a spy scandal.
Mr Juncker - Europe's longest-serving head of government - submitted his resignation to Grand Duke Henri.
The grand duke will now take his time to decide when to dissolve parliament and call new elections, officials say.
The government collapsed after junior coalition partners withdrew their support, claiming the intelligence service was out of control.
They say Mr Juncker failed to stop illegal security agency activity such as phone-taps and corruption.
He has been prime minister since 1995 and was head of the Eurogroup of eurozone finance ministers between 2005 and January 2013 - a period that included the height of the eurozone crisis.
'Hopes to return'
Mr Juncker met with Grand Duke Henri on Thursday to discuss the possibility of calling early elections.
This followed a meeting with government where it was reportedly suggested that the government and parliament would remain in place until October, when elections might be held.
Mr Juncker told reporters on Thursday that he "very much" hoped to run again, but was waiting for the go-ahead of his centre-right Christian Social Party (CSV).
The political crisis unfolded after a parliamentary review into allegations of misconduct by the country's SREL security agency.
They included claims of illegal bugging of politicians, the purchase of cars for private use and payments in exchange for access to local officials.
The review concluded that "the prime minister, as head of the intelligence service, not only had no control over his service but also too often omitted to inform the parliamentary control committee or the judiciary of its irregularities, aberrations and illegalities".
The report was commissioned after a Luxembourg newspaper published a secretly-taped conversation from 2008 between Mr Juncker and the head of SREL at the time, Marco Mille.
Mr Mille revealed that his staff had secretly recorded a conversation involving the grand duke and that the sovereign was in regular contact with Britain's MI6.
Mr Juncker has denied any wrongdoing but has faced criticism that he focused too much on his eurozone duties.
But his coalition partner, the Socialists (LSAP) withdrew their support for the prime minister, demanding new elections.
As head of state, only the grand duke can officially dissolve parliament. The current government would then remain pending elections, but it would be unable to put forward any legislation.