The frontrunner in South Korea's presidential race could be beaten if his two rivals go ahead with a plan to unify their campaigns, a poll has shown.

Conservative Lee Hoi-chang has been consistently leading opinion polls.

But a poll published on Tuesday indicated that millionaire Chung Mong-joon or former human rights lawyer Roh Moo-hyun could win if one stepped aside.

The presidential election will be held on 19 December to find a successor to the incumbent leader Kim Dae-jung, who must stand down after a five-year term.

Among other issues at stake in the election is South Korea's 'sunshine policy' of engaging with the reclusive North.

The policy has been put under severe strain by Pyongyang's alleged admission that it has nuclear weapons.

Although all candidates have called on North Korea to scrap its nuclear programme, Mr Lee has called for financial aid to Pyongyang to be halted until its arms ambitions can be clarified.

Survey results

The survey of 1,000 people commissioned by Munhwa Ilbo newspaper and YTN cable news network found that the Grand National Party's Mr Lee is leading a three-man race with 41.1%, against 27.9% for Mr Chung and 23.9% for Mr Roh.

Lee Hoi-chang takes a harder line on the North

But it showed that if either Mr Roh or Mr Chung stepped aside and backed the other, they would take the lead.

Mr Chung has a lead over Mr Lee of at least 10 percentage points, and Mr Roh is favoured over Mr Lee by a margin of 46.2% to 42.2%.

Mr Roh, the candidate for the ruling Millennium Democratic Party, and Mr Chung, who has recently formed the National Alliance 21, agreed on Saturday to merge their campaigns.

They decided to narrow the field through a televised debate and public opinion survey, with the loser promising to campaign for the victor against Mr Lee.

Campaign snag

But the two camps have since been mired in arguments over the selection process, which must be completed before a 28 November deadline to register a candidate.

Despite the electorate surveyed apparently preferring a candidate running on a joint Chung/Roh ticket, 54.5% of those polled said they nevertheless believed Mr Lee would win the race.

Meanwhile, North Korea has made it clear it does not want Mr Lee to win.

"Lee is desperately tightening the bridles of the nuclear war chariot, while trumpeting about co-operation for the implementation of the US war policy," the North's party daily Rodong Sinmun said on Tuesday.