Seoul: South Korean truckers extended their strike on Friday after talks on higher pay and demands for cheaper diesel broke down, threatening to further dent government efforts to boost the country's export-dependent economy.

More than 14,000 truckers throughout the country are expected to join the walkout, which began unofficially earlier in the week. About 4,000 truckers took part on Thursday and a number of unions are planning a formal strike vote later on Friday.

A union official said truckers had nothing to lose by refusing work and pay that already fell short of the costs of operating their vehicles after sharp rises in global oil prices.

The government said it will mobilise military trucks and schedule more cargo rail services to keep the country's factories running and goods for export moving to the ports.

The Transport Ministry said it would immediately revoke striking truckers' annual fuel subsidy payments of about 15 million won ($14,500), and will begin providing police escorts to non-striking vehicles.

The strike adds to President Lee Myung-bak's woes as he tries to calm more than a month of massive public protests over a deal his government signed with the United States to resume imports of US beef.

The protests have grown and changed in focus. Labour groups and left-leaning activists have seized on the protests as a chance to criticise Lee's economic reform plans.

The militant umbrella Korean Confederation of Trade Unions is planning to hold a strike vote on Friday and its member unions, including the Hyundai Motor union, are expected to hold their own strike votes in coming days.

Shipping stocks were down in early Friday trading, but transport shares, manufacturers and steel makers were up in line with the broader market's 1 percent rise.