Greece's leftist Syriza party has a 0.6 percentage point lead over the conservative New Democracy party, a Kapa Research poll for To Vima newspaper showed on Thursday.
The poll showed Syriza was set to get 29 per cent of the vote in a national election on Sept. 20, while New Democracy would get 28.4 per cent.
Most surveys over the last two weeks have put the two parties virtually neck and neck.
The poll was conducted between Sept. 15-16, meaning it took account of voter reactions to Monday's televised debate between the parties' leaders - ex-prime minister Alexis Tsipras of Syriza and Vangelis Meimarakis of New Democracy.
A previous survey by the same pollster on Sept. 12 had shown Syriza had a 0.5 percentage point lead.
The Kapa survey showed the far-right Golden Dawn party ranking third with 6.7 per cent, followed by the socialist PASOK party and the communist KKE party. It put undecided voters at 7.4 per cent.
The poll showed the Independent Greeks party, the junior partner in the previous coalition government, barely making it into parliament with support at the 3.0 per cent entry threshold.
Two opinion polls published on Wednesday differed ahead of Sunday's national election, with one giving leftists a four percentage point lead over conservatives and the other putting the conservatives marginally ahead.