UPDATE 1-Romanians vote in poll that may reopen political spat
* Heavy snow, fog delays some voting
* Leftist governing alliance may win majority
* President could appoint a different PM
* Political uncertainty could hit markets
(Adds polls opening, bad weather, comment)
BUCHAREST, Dec 9 (Reuters) - Romania's prime minister was headed for victory in parliamentary elections on Sunday that could set off another round of a power struggle with the rightist president and complicate talks for a new IMF deal.
Victor Ponta's leftist Social Liberal Union (USL) will win the most votes and possibly a clear majority, opinion polls showed. But analysts said President Traian Basescu might use his powers to ask one of his own allies to try to form a government.
Any prolonged period without a new administration in place would unnerve markets and raise questions about how Romania would obtain a new International Monetary Fund deal once the current agreement expires in early 2013.
Heavy snow, rain and fog across the Balkan country delayed the opening of some polling stations but Ponta said all citizens were able to cast ballots. Polls will close at 9 p.m. (1900 GMT) with first results due early on Monday.
"I am convinced that today Romania will write a new page in its history and things will get better," he said in his Targu Jiu constituency, a mining town a few hours from Bucharest.
The former communist country has made progress in some areas since the 1989 revolution that overthrew dictator Nicolae Ceausescu, but although it joined the European Union in 2007, it remains the bloc's second poorest member.
Romania lags regional peers Poland, Hungary and the Czech Republic and struggles to supply running water and reliable electricity to some of its 19 million people. Long-term reforms such as privatisation of inefficient state companies and an overhaul of health care have failed to materialise, and the economy is struggling to recover from a deep recession.
The leu fell to a record low against the euro in August during an attempt by Ponta to remove the conservative Basescu from office, using tactics which the EU and United States said undermined the rule of law.
At the time, Basescu said he would never again name Ponta as prime minister. This week, he said only that he would appoint someone in the best interests of the country.
The USL has benefited from disenchantment with Basescu and the previous government, which pushed through unpopular austerity measures such as salary cuts and higher sales tax. But lacklustre economic growth will give the next administration little room to ease cost cuts and tax rises.
"I gave a chance to the team which is now ruling (USL)," said former textile worker Doina Isopescu, speaking in freezing rain outside a polling station in a communist-era Bucharest neighbourhood. I'm fed up with cuts, cuts and again cuts."
The USL has scored at least 57 percent in three opinion polls published in December and Romania's complicated electoral system - combining constituencies and proportional representation - favours large parties.
One possibility would be for Basescu to ask someone other than Ponta from within the USL to become prime minister, using the argument that it is a coalition of different political groups rather than a party, according to analysts.
If the USL falls short of a majority, he could also ask an ally from the Right Romania Alliance (ARD) - in second place in polls with about 20 percent - to try to form a coalition.
"It is unlikely that the process of electing a new cabinet will be a smooth one and we expect temporary leu depreciation and higher leu yields until Romania has a new government," said UniCredit analyst Dan Bucsa.
Less than half of electorate, estimated at 18.3 million, was likely to vote, analysts said, due to a deep dissatisfaction with politicians, many of whom voters view as corrupt.
"Romania's political class is all horrible," said Anton Popescu, who lives off a pension of 900 lei ($250) a month. "I have no hope for better times after the election. I just hope it won't be worse than it already is."
(Reporting by Sam Cage; Editing by Mark Heinrich)