Washington has urged North Korea not to escalate tensions in the Yellow Sea following a naval skirmish between the North and South Korean navies Tuesday.
White House press secretary Robert Gibbs says Washington hopes Pyongyang will not take any further actions in the area that could be seen as an escalation.
South Korea's military says one of its warships first fired warning shots at a North Korean boat that it says crossed the Korean maritime border off the west coast of the Korean peninsula.
South Korea says the North Korean patrol boat suffered heavy damage in the exchange before retreating. A South Korean military official described the incident as regrettable and said Seoul has lodged a strong protest with Pyongyang.
North Korea's official news agency says its patrol boat was on a mission to confirm an unidentified object on its side of the border.
North Korea demanded that South Korea apologize for what it called a grave armed provocation.
South Korea says it suffered no casualties. It is not clear if anyone on the North Korean boat was hurt.
U.S. President Barack Obama is due to make a two-day visit to South Korea next week as part of his tour of Asia. One issue high on his agenda is international efforts to dismantle North Korea's nuclear weapons program.
Last month, North Korea's navy accused South Korea of sending warships across the maritime border to stir up tensions and warned that such actions could trigger armed clashes.
North and South Korea fought two deadly naval battles in the Yellow Sea in the past decade.
Some information for this report was provided by AFP and Reuters.