* Election pits pro-West rulers against powerful communists
* Outcome difficult to read after September referendum flop
* Relations with Russia and Romania at stake
(Adds quote from Filat, details of poll)
By Alexander Tanas
CHISINAU, Nov 26 (Reuters) - Moldova holds its third parliamentary election in little more than a year and a half on Sunday, which could decide whether the ex-Soviet republic sticks to a pro-Europe course or opts for closer ties with Russia.
Its four million election-weary people will be trying yet again to break a stalemate that has left it without a full-time president since mid-2009.
The election, in a country where former Soviet master Russia and European Union neighbour Romania vie for influence, will be a test of how well a four-party ruling coalition has sold a pro-Europe message since taking power 15 months ago.
The Alliance for European Integration has sought to move Moldova, one of Europe's poorest states with an average monthly salary of $230, closer to mainstream European institutions.
It is trying to make itself eligible for EU membership one day by improving crumbling infrastructure and government services through funding and aid projects from abroad.
"The only true chance for Moldova is to continue with the reforms that have begun and which are supported by its external partners -- the EU, the United States, the IMF and the World Bank," Prime Minister Vlad Filat told Reuters. "Our main aim is not to allow the return of Moldova to the past."
While Romania and other EU states hope the coalition will remain in power, Russia may be counting on the emergence of a left-centrist coalition, including the communists, to end a gradual slide in relations since the Alliance came to power.
Though Moldova relies exclusively on Russia for its gas, it fell foul of Moscow when acting president Mihai Ghimpu fixed a "Day of Soviet Occupation" in the political calendar.
Russia responded with restrictions on imports of Moldovan food, including wines which are Moldova's main export earner.
The unreliability of opinion polls in Moldova makes the election difficult to call. Last September, surveys showed the Alliance would coast through a referendum for direct elections for president -- but the poll collapsed on low voter turnout.
Many commentators say the election is unlikely to change the balance of the parties and say neither side will get enough seats to break the impasse. Polls open at 7 a.m. (0500 GMT) and close at 9 p.m. (1900 GMT) on Sunday.
PAST VIOLENCE
Opinion polls show that the popularity of the opposition communists, the biggest single party, is declining while the ratings of two coalition parties -- Filat's and that of former presidential candidate Marian Lupu -- are on the rise.
When the communists declared victory in a April 2009 election, young people in Chisinau ransacked the president's office and parliament building. The communists lost to the coalition in a snap election in July that year.
While support for the coalition parties is strong in the cities, a deep nostalgia for Soviet times works to the advantage of the communists in rural areas.
The communists, led by former President Vladimir Voronin who had called for a boycott of the referendum, hailed the outcome as a sign that public sentiment is moving back in their favour. Voronin, twice president, drew sneers from the coalition when he turned down a challenge to a TV debate on the eve of the vote. "I did not think he was that much of a coward," Filat said in a statement on Friday.
The Alliance at present holds 53 seats to the communists' 48 -- and was twice unable to win over enough defectors to get the required 61 votes in parliament to vote Lupu in as president.
"The future parliament will look a lot like today's and so these elections are not likely to take Moldova out of crisis. In general the balance between the Communist party and other parties will remain," said analyst Bogdan Tirdea.
Other commentators said the communists could form a left-centre coalition with Lupu, who has close ties with Russia, should he decide to quit the Alliance. (Writing by Richard Balmforth, editing by Maria Golovnina)