* Target likely equivalent to 4 pct below 2005 levels

* At strongest level recommended for developing countries

* Seen readying country for carbon tariffs

(Adds more details)

By Cho Mee-young

SEOUL, Nov 17 (Reuters) - South Korea has set its voluntary 2020 emissions reduction target to a 30 percent reduction from its forecast under a "business as usual" scenario, the presidential office said in a statement on Tuesday.

"Unless there is a big change in the business situation, the business as usual target should be equivalent to a 4 percent reduction (against 2005 levels)," Woo Ki-jong, secretary-general of the presidential committee on green growth, told Reuters by telephone.

The OECD's fastest-growing carbon polluter earlier this month ditched its weakest voluntary emissions target of an 8 percent increase from 2005 emissions levels by 2020. [ID:nSEO156452]

A senior government source said on Saturday South Korea had adopted the toughest of its two voluntary 2020 emissions reduction targets -- either unchanged from or 4 percent below 2005 levels ahead of a global meeting in Copenhagen.[ID:nT242854]

President Lee Myung-bak said in the statement that while emissions reduction would present "short-term burdens" it would also bring "broader national gains."

"Through the aggressive greenhouse gas reduction, South Korea will be ready for industrialised countries' carbon trade tariffs, raise energy security and acquire market share first in rapidly growing green sectors."

While not obliged under the U.N.'s Kyoto Protocol climate pact to announce binding cuts, South Korea faced pressure to put the brakes on the rapid growth of its planet-warming emissions from industry and transport.

The statement noted that the target cut was the strongest recommended to developing countries by the Intergovernmental Panel on Climate Change.

South Korea's green investment plans are already among the most ambitious in Asia, with the government saying earlier this year it would pump 107 trillion won ($92.88 billion) into environment-related industries over the next five years.

The country is hoping to showcase its green policies when it hosts a G20 summit next year. ($1=1152.0 Won)

(Editing by Jonathan Hopfner)

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