Sounding like a man in a hurry, Lee Myung-bak became South Korea's new president on Monday promising pragmatism over ideology to achieve his most pressing task - reviving the economy.

His inauguration speech was packed with pledges taken from his campaign for December's election which he won by a landslide to end 10 years of liberal rule marred by slow economic growth.

"Although it is going to be difficult and painful, we must change much more and much faster," the 66-year-old conservative told an estimated crowd of 60,000 people that included Japanese Prime Minister Yasuo Fukuda and U.S. Secretary of State Condoleezza Rice.

"Economic revival is our most urgent task," he said, vowing to seek out new engines of growth to raise the economy and create more jobs, promising to ditch what he called the ideology of the outgoing government and replace it with pragmatism.

Lee, a prominent ex-construction company boss whose move into politics included a popular stint as Seoul mayor, said the world's 13th largest economy was at a crossroads and urged South Koreans to be more positive to change.

In reference to the labour strife that has plagued the economy for years, he pressed both unions and management to cooperate more.

And he pledged to free the economy of bureaucracy and make life easier for businesses which complain that they were stifled under the previous liberal government.

Lee, whose campaign focused largely on promises to nearly double the country's economic growth, said South Korea must also be more open to the outside world.

The ceremony, the start of which was hosted by two popular comedians, included traditional music and a nod to more modern tastes with a performance by a group of breakdancers. It was due to end to the sound of Ludwig van Beethoven's "Ode to Joy".

Lee underscored his campaign promise to improve relations with the United States, which maintains close to 30,000 troops in the South but with whom relations in recent years have at times been prickly.

NORTH TIES

On his likely biggest diplomatic challenge - how to deal with North Korea - the new president said relations between the two must be more productive and repeated past pledges to help his communist neighbour raise its economy only if it ends its nuclear weapons programme.

"Together, the leaders of the two Koreas, must contemplate what they can do to make the lives of all 70 million Koreans happy and how each side can respect each other and open the door to unification.

"If it is to discuss these issues, then I believe the two leaders should meet whenever necessary and talk openly, with an open mind."

There was no North Korean representative at Lee's inauguration and its state media has made no direct mention of the election of Lee who has made clear he thinks the outgoing government was too soft on the isolated North.

A father of four, Lee's rags-to-riches life story made it to two hit TV dramas about business heroes who raised the country out of the ashes of the 1950-53 Korean War.

He has had a bumpy ride since winning the election, clashing early on with one of the main labour unions and teacher groups.

He has also had settle for a compromise over his proposed cabinet after a fierce challenge from liberal MPs who still dominate parliament.

That is a situation Lee hopes will change in the April parliamentary election when his conservative party is tipped to win a majority that will give him the political muscle to push through new policy.