Moldovan voters will head to polling stations on September 5 in a referendum to change the country's constitution to end the year-long political logjam, caused by parliament's inability to elect a president.

The referendum proposed a change in article 78 of the country's constitution, envisioning the president being elected by popular vote, as the country did since declaring independence in 1991 and until constitutional amendments were passed in 2000.

Moldova's pro-Russian communist party won the parliament elections in 2001 and 2005 by a margin sufficient to elect party leader Vladimir Voronin president. It won again the vote in April 2009, which sparked a day of rioting in capital Chisinau and the torching of the parliament and presidency buildings, as opposition parties accused the communists of rigging the elections.

The communists fell one MP short of the 61-seat majority needed to elect a president and did even worse during the July 2009 snap elections, when it was reduced to 48 MPs, still the largest party in the 101-seat parliament and enough to block a presidential election.

But Moldova's ruling Alliance for European Integration, made of four parties previously in opposition, decided to eliminate future political stand-offs by amending the constitution, rather than call new snap elections. Parliament speaker Mihai Ghimpu has been acting president since his election in September 2009.

The leaders of all four parties that make up the ruling coalition asked voters to go to the polling stations, but communist leader Voronin, who is no longer eligible to run for president, said that it was a "trap" and asked voters to boycott it.

He said the ruling coalition would not stop if victorious: "A second referendum will be about Moldova's exit from the Commonwealth of Independent States and the third one about union with Romania. Then it will be about joining Nato and there will be nothing left of the country," he said, as quoted by news website Unimedia.

Voronin and the communists have repeatedly tapped the fears of Moldova's large Slavic ethnic minorities about a possible union with Romania to solidify support in the past. He went as far as to accuse Romania of orchestrating the riots in April 2009, further straining diplomatic relations with Bucharest.

But the referendum would only need 33 per cent turnout to be validated, under new rules passed by parliament. The ruling coalition also counts on increased support from Moldovans living abroad, mostly migrant workers, increasing the number of polling stations to include new areas that are far away from embassies and asking the election authorities to allow Moldovans with expired identification papers to vote in the referendum, a request that has been granted.