Greece has brought forward to this month the date of its next presidential election, which is conducted by the country's parliament.
The announcement came after eurozone ministers approved a Greek request for a two-month extension to its bailout programme, due to end later this month.
The presidential vote on 17 December will be a vital test for embattled Prime Minister Antonis Samaras.
His decision prompted the stock market in Athens to plummet 9.5% on Tuesday.
Analysts said the markets had been spooked by the risk of snap elections, which will take place if the conservative-led government's nomination is not approved by parliament.
President Karolos Papoulias's five-year term ends in March, and a vote had been expected in February.
Mr Samaras's conservative-led coalition needs the support of other parties if its candidate is to obtain the backing of MPs.
But the left-wing anti-bailout Syriza party is leading in the opinion polls and the government faces widespread public discontent after a six-year recession.
Hours after saying he would bring forward the presidential vote, Mr Samaras gave a televised address announcing that his coalition was nominating former European Commissioner Stavros Dimas as its candidate.
"When the current parliament elects a president at the end of the month the clouds will be gone and the country will be ready to officially enter the post-bailout era," the prime minister said, linking the vote in parliament to the end of the unpopular programme of support from the EU and IMF.
Since 2010 Greece has received almost €240bn (£190bn; $295bn) in rescue funds, which are due to be replaced next year by a new eurozone credit line that can be accessed in an emergency.
Syriza's leader Alexis Tsipras accused the government of rushing it through in a "desperate attempt" to hide new austerity measures. He has pledged to end austerity cuts and any co-operation with either EU or IMF lenders.
Mr Samaras's government narrowly pushed through its 2015 budget in the early hours of Monday, securing 155 votes in the 300-seat parliament.
But if it is to convince MPs to back its presidential candidate it will need far greater support from the chamber.
Two hundred MPs are needed to back a candidate in the first or second vote, and 180 for the third vote. The second and third rounds of the vote are scheduled for 23 and 29 December.
Mr Samaras will have to secure the backing of 25 opposition lawmakers to reach 180 votes.
Monday's move to extend the bailout and advance the date of the presidential vote came a day after violent protests in Athens, with more than 300 demonstrators arrested.
The demonstration was held to mark six years since police shot dead an unarmed teenager during protests fuelled by anger over the country's economic crisis.
"The coming period is essential to find an agreement [with the eurozone] to settle issues like the debt, and Greece has to have the full capacity to mobilise its forces in a climate of national unity and political stability," the government said in its statement.
Some investors are worried about a return to the days of financial crisis as the presidential vote looms.