(Releads, adds GM Daewoo's vote for strike, para 8-10)
By Kim Kyoung-wha
SEOUL, June 30 (Reuters) - The union for workers at South Korea's top car maker, Hyundai Motor Co , said it would extend a four-day strike if its demands for a wage hike and a big profit bonus were not agreed to in talks on Wednesday.
The country traditionally faces a seasonal rise in union action every summer, but labour unrest this year poses a big headache for a government struggling to bolster sluggish local demand and business spending.
Foreign investors also cite labour strife as part of the reason for the low value of local stocks, known as the "Korea discount."
"Negotiations are underway now," Chang Gyu-ho, a union spokesman at Hyundai Motor. "The outcome of the talks will be available after 5 p.m. (0800 GMT)."
"If the final offers are not satisfactory, we would have no other choice but to launch a longer-term strike," he said.
The union is demanding a 10.48 percent wage hike and a bonus worth 30 percent of the company's profit. If agreed, this would lift average Korean auto worker pay rates to $27 an hour, above their U.S. peer's $26 an hour.
Analysts have said prospects for a relatively short strike had buoyed Hyundai's share price. A strike at Hyundai last year went on for 45 days. Although they also said a long strike could help Hyundai reduce high inventories of unsold cars, particularly for the depressed local market where consumers are reluctant to spend because of heavy credit card debts.
Shares in Hyundai Motor ended jumped four percent to end at 44,450 won, outperforming a 0.91 percent rise in Seoul's main board .
Hyundai's 40,000 unionised works held six-hour strikes on Friday and Monday, before staging full day-long strikes on Tuesday and Wednesday.
A combined 110,000 workers at Hyundai Motor and smaller auto makers, textile companies, department stores and other workplaces downed tools on Tuesday.
LOST PRODUCTION
The union at unlisted GM Daewoo Technology Automotive and former Daewoo Motor's Pupyung plant voted on Wednesday to strike with 65 percent support, a union official said. But the union has yet to decide when to go on the strike, he said.
The strike could dampen prospects for General Motors Corp's plan to take over the plant, which was left out of the the U.S. firm's acquisition of the bankrupt Korean car maker in 2002.
GM wants to see progress in areas such as labour stability and productivity before buying the plant.
As of Tuesday, the strike at Hyundai Motor and smaller rivals has cost 161.5 billion won ($140.3 million) or a combined 11,559 vehicles in lost production, according to company data.
Ssangyong Motor Co > said the country's sports utility vehicle maker resumed operations on Wednesday after a four-hour strike a day earlier.
($1=1151.0 Won)