As marathon negotiations by senior officials from the rival Koreas stretched into a third day, South Korea's president said Monday that anti-Pyongyang propaganda broadcasts will continue unless North Korea apologizes for planting land mines that maimed two South Korean soldiers.

The comments by Park Geun-hye suggest both a hard line stance and mounting frustration in Seoul. Her comments provide hint at why the talks, which started Saturday evening have dragged on into a second session that began Sunday afternoon and was still going 24 hours later, on Monday.

For the time being, the diplomacy has pushed aside previous heated warnings of imminent war, but South Korea's military said North Korea continued to prepare for a fight, moving unusual numbers of troops and submarines to the border.

North Korea is refusing to apologize for what Seoul says was a land mine attack earlier this month and then an artillery barrage last week. North Korea denies both attacks and demands that Seoul stop the propaganda broadcasts started in retaliation for the land mine explosions.

These are the highest-level talks between the two Koreas in a year. And just the fact that senior officials from countries that have spent recent days vowing to destroy each other are sitting together at a table in Panmunjom, the border enclave where the 1953 armistice ending fighting in the Korean War was agreed to, is something of a victory.

The length of the talks — nearly 10 hours for the first session and more than 18 for the second — and the lack of immediate progress are not unusual. While the Koreas often have difficulty agreeing to talks, once they do, overlong sessions are often the rule. After decades of animosity and bloodshed, however, finding common ground is much harder.

President Park said during a meeting with top aides that Seoul would not "stand down even if North Korea ratchets up provocation to its highest level and threatens our national security."

She said Seoul needs "a definite apology" and a promise that such provocations would not recur.

Yoo Ho-yeol, a professor of North Korean studies at Korea University in Seoul, said the unusually long session was a good sign. "They are not talking for the sake of a breakdown but for the sake of agreement. There must be a lot of fine-tuning and convincing between the two parties," Yoo said.

The decision to hold talks came hours ahead of a Saturday deadline set by North Korea for the South to dismantle the propaganda loudspeakers. North Korea had declared that its front-line troops were on war readiness and prepared to go to battle if Seoul did not back down.

South Korea said that even as the North was pursuing dialogue, its troops were preparing for battle.

An official from Seoul's Defense Ministry said that about 70 percent of the North's more than 70 submarines and undersea vehicles had left their bases and were undetectable by the South Korean military as of Saturday. The official, who refused to be named because of official rules, also said the North had doubled the strength of its front-line artillery forces since the start of the talks Saturday evening.

South Korean military officials wouldn't confirm or deny but seemed to cast doubt Monday on a Yonhap news agency report, citing unidentified military sources, that said North Korea had moved toward the border about 10 hovercraft used for landings by special operation forces in the event of a war.

Defense Ministry spokesman Kim Min-seok said the truth is "a bit different" than what was reported but wouldn't provide further details.

Meanwhile, the United States, which has 28,500 soldiers based in South Korea, is conducting annual joint military exercises with the South. North Korea regularly condemns the maneuvers as a preparation for war.