TOKYO - TWO candidates vying for a governor's post were in close competition on Sunday in a race seen as a key factor for influencing when embattled Prime Minister Taro Aso will call a general election.

Mr Yukiko Sakamoto backed by Mr Aso's Liberal Democratic Party (LDP) and Mr Heita Kawakatsu supported by the main opposition party were running neck and neck, according to exit polls by public broadcaster NHK.

Four candidates were vying to replace the retiring governor of central Shizuoka prefecture, with results now expected early on Monday rather than Sunday because of the close contest, officials said.

It is one of two polls that will likely influence Mr Aso's decision on the timing for a general election he must call by September. The other is the Tokyo assembly election on July 12.

Mr Kawakatsu is supported by the main opposition Democratic Party of Japan (DPJ).

If Mr Sakamoto loses, it would be a setback for Mr Aso, whose poll ratings have plunged below 20 per cent.

The premier, who has been in office less than a year, already faces mounting pressure from within his own party to quit the leadership so a new face can lead it into the general election.

Many pundits agree that the LDP, having lost the upper house in 2007, is likely also to lose its large majority in the powerful lower house to the DPJ. -- AFP