South Korea ? South Korea’s troops went on high alert today for possible retaliation by North Korea after one of its navy ships was nearly destroyed and an officer reportedly killed in a skirmish with the South, ahead of a visit by President Barack Obama.

The clash Tuesday along the disputed western sea border was the first such engagement in seven years, sending tensions soaring about a week before Obama travels to Seoul as part of his Asian tour.

The exchange of fire also occurred just hours before the State Department announced a senior U.S. diplomat will travel to North Korea before year’s end to try to entice North Korea back into international negotiations on nuclear disarmament. The dispatch of envoy Stephen Bosworth would mark the first direct talks between Washington and Pyongyang since Obama took office in January.