The two Koreas traded threats on Friday following a brief exchange of fire a day earlier, in a confrontation that experts say carries a risk that the inexperienced North Korean dictator Kim Jong Un will provoke South Korea to launch a major military retaliation.
The standoff is the first major test of Mr. Kim�s ability to handle a military clash with South Korea along the heavily armed border.
In a step up from smaller border skirmishes last year, North Korea launched rockets on Thursday into remote areas over the border in response to anti-Pyongyang propaganda that South Korea has been blasting across the frontier through speaker systems. Seoul responded by firing dozens of artillery rounds at North Korean bases.
On Friday, South Korea�s military said in a letter to its northern counterparts that it was prepared to �strongly retaliate� to any further attacks after North Korea had threatened to attack the loudspeakers unless they are turned off by Saturday afternoon. Seoul continued its broadcasts Friday and gave no indication it would meet the North Korean demand.
With neither side showing signs of backing down, the question Friday was whether the confrontation would escalate.
�Both sides are playing with fire in this crisis,� said Go Myung-hyun, an expert on North Korea at the Asan Institute for Policy Studies, a Seoul-based think tank.
The U.S. military in South Korea, which is now conducting annual summer drills with South Korean forces, said it was monitoring the situation. North Korea often raises its level of aggressive rhetoric during the exercises.
At a briefing on Thursday, U.S. State Department spokesman John Kirby said Washington called �on Pyongyang to refrain from actions and rhetoric that threaten regional peace and security.�
In one indication that the situation hasn�t yet tipped into full-blown crisis, young South Koreans on Friday played a rare soccer match in the North Korean capital. A team representing a South Korean province beat a squad from the Chinese city Kunming 3-0, South Korea�s Yonhap News Agency reported.
Mr. Kim, believed to be 32 years old, took power in North Korea at the end of 2011. He is frequently shown in state media directing military drills and rocket launches. But his ability to manage military engagement is unclear. Frequent changes in top military staff have also raised questions among outsiders about Mr. Kim�s strategic goals and the level of expertise of those that surround him. Earlier this year, Mr. Kim purged his defense minister, the fourth person to hold the job under the North Korean leader.
North Korean state media reported that Mr. Kim chaired a meeting of generals late Thursday and ordered the military to be on a �semi-war state� as of Friday, one of the country�s highest states of alerts. In Pyongyang, propaganda trucks with loud speakers broadcast news about the raised level of alert, according to an Associated Press report from the North Korean capital.
Escalating the perceived level of threat inside North Korea also helps to bolster support for Mr. Kim, experts say.
The stakes for North Korea are higher since Seoul loosened its rules of engagement to allow quicker, more powerful responses to North Korean aggression. The shift came after a 2010 North Korean artillery attack on a South Korean island that killed four people and led to the resignation of South Korea�s defense minister, criticized for a weak response.
North Korea�s tactics so far appear to come from a military playbook it has used successfully for decades. Its attacks are often calibrated to maximize fear but avoid a descent into a major conflict its inferior military can�t win, experts say.
Thursday�s shells from the North landed in a remote area, so causing no loss of life�but generating concern in South Korea that further violence could follow. Pyongyang�s setting of a Saturday deadline is also a familiar gambit to increase anxiety and pressure from some inside South Korea to compromise.
One potential route out of the crisis is an offer of talks sent by North Korea late Thursday. However, South Korea�s Unification Ministry, which coordinates inter-Korean relations, said it didn�t consider the offer sincere because Pyongyang denied both launching rockets at the South and planting land mines that maimed two South Korean soldiers earlier this month.
It was as a response to the mine incident that South Korea resumed the loudspeaker broadcasts after more than a decade. Pyongyang is particularly sensitive to the broadcasts because they include criticism of Mr. Kim, an act of treason under the country�s cultlike political system.
�Jeyup S. Kwaak contributed to this article.