The Washington Post says concerns are rising in the U.S. over President Lee Myung-bak’s shift toward a hawkish stance regarding North Korea following the North’s artillery attack on Yeonpyeong Island last month.

The U.S. daily said the latest provocations from North Korea and the resulting rightward swing in South Korean public opinion have transformed the South Korean president’s strategy for dealing with the North. The daily said that if Lee’s old method was “act with caution,” his new method is “get tough.”

The report said Lee's shift in thinking has prompted modest but growing concern in the Obama administration, where officials worry that an overly aggressive South Korea could become a liability.

The paper said that though several U.S. officials defended Seoul's plans to hold live-fire drills from Yeonpyeong Island last week, U.S. Joint Chiefs of Staff Vice Chairman James Cartwright worried that the artillery drills could set off a "chain reaction," in which U.S. and South Korean forces "lose control of the escalation."

According to the report, political analysts in Seoul and Washington predict that Lee will soon face pressure from the United States to reengage diplomatically with the North.