IN SEOUL The latest provocations from North Korea and the resulting rightward swing in South Korean public opinion have transformed South Korean President Lee Myung-bak's strategy for dealing with the peninsula's troublemaker. The old method: Act with caution. The new method: Get tough.

Lee's shift in thinking has prompted modest but growing concern in the Obama administration, where officials say they worry that an overly aggressive South Korea could become a liability in its own right.

Political analysts here and in Washington predict that Lee will soon face pressure from the United States to reengage diplomatically with the North. But Lee has turned increasingly hawkish in recent weeks after taking criticism for Seoul's weak initial counterattack to Pyongyang's Nov. 23 shelling of Yeonpyeong Island.

"Fear of war is never helpful in preventing war," Lee said Monday in a radio address. "If we are firmly determined to brave any risks, we can fend off any emerging threats."

Policymakers here have long debated the best North Korea policy, finding downsides to every solution. Lee faces domestic pressure to remain firm and international pressure to reduce tension on the peninsula. Of late, Lee has given priority to the first of those demands. But with two years left in his term, how he meets what one Western diplomat called the legacy-defining challenge of "putting North Korea back into the box" will shape security in South Korea, where the United States stations 28,500 troops.

Lee recently overhauled the rules of engagement, making it easier to respond with greater force against the North. He also installed a new defense minister, Kim Kwan-jin, who called for additional airstrikes if the North attacks again. Lee visited South Korean troops last week, telling them that future aggressions from Pyongyang would require a "powerful counterattack." Lee also said his old beliefs were mistaken. "We thought we could keep this land peaceful with tolerance," Lee said, "but it was not true."

A history of tepid responses



Another move by the North is precisely what some analysts expect.

"It makes no sense to think we've seen the last of North Korea's provocations," said Bruce Klingner, a former North Korea CIA analyst and current researcher at the Heritage Foundation. "So now you have North Korea driven to additional provocations and Lee Myung-bak driven to respond more forcefully - even if it leads to conflict. When you have that situation, you're much more likely to have a miscalculation."

For years, South Korea had responded to North Korea's occasional belligerence by backing down, a means to preserve the many things it could lose in a war: its capital city, its thriving economy, its infrastructure. Even after North Korea torpedoed a South Korean warship in March, killing 46, Lee's most noteworthy proposal - blasting propaganda messages at the border - was dropped when Pyongyang threatened to shoot the loudspeakers.

But then came the shelling of Yeonpyeong Island, where four South Koreans died and 18 were injured. The attack exposed an underbelly in Seoul's readiness, and when the South Korean military counterattacked, it did so with a pinch, not a punch. Lee had to apologize for the feeble showing. One poll a short time later suggested that 65 percent of South Koreans wanted a tougher policy against the North, and Lee, according to political analysts, has been trying to belatedly meet that demand.

Switching gears



On Dec. 16, South Korea announced it would hold an artillery drill on Yeon-pyeong - a regular practice, yes, but a symbolic show of force on demolished, disputed territory. The next day, Pyongyang promised a catastrophic retaliation.

Although several U.S. officials defended Seoul's plans, Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, voiced worry that the artillery drills could set off a "chain reaction," in which U.S. and South Korean forces could "lose control of the escalation."