Major issues will be the peace process and cost of living

UNP chairman K Jayasuriya

A key issue is likely to be the proposal to change the country's constitution and devolve greater power to the regions.

The president's order comes into effect from midnight on Friday.

Candidates will have to file their nominations with the election commissioner between 28 August and 4 September.

The BBC correspondent in Colombo, Alastair Lawson, says campaigning is expected to be acrimonious and will focus on the 17-year-old war with Tamil separatists.

"Major issues will be the peace process and cost of living," UNP chairman, Karu Jayasuriya, told the Reuters news agency.

"Devolution proposals are an emotional and important issue," he added.

Devolution

Earlier this month, President Chandrika Kumaratunga was forced to back down on a draft constitution bill, after failing to gain enough support in parliament.

The PA campaign will be led by Ratnasiri Wickremanayake

The president argued that the bill was the only way to end the conflict with Tamil Tiger rebels in the north and east.

The devolution package would have given Tamil majority areas greater power in running their own administration.

The plan has been rejected by the Tamil Tigers, who are fighting for a separate Tamil homeland.

It has also been bitterly opposed by nationalist organisations and the influential Buddhist clergy, who regard it as divisive.

The UNP and other opposition parties rejected the plan, saying it had been hurried through.

The PA's campaign will be led by Prime Minister Ratnasiri Wickremanayake, who replaced the president's mother and veteran leader Sirimavo Bandaranaike last week.

If the UNP wins a majority, President Kumaratunga will face the prospect of having to work with a hostile parliament.

She has suggested that the new parliament be turned into a constituent assembly to pass the draft constitution by a simple majority, if the government fails to get the two-thirds majority it needs to pass it.