North Korea's military rejected Thursday a South Korean appeal to ease rising tensions on the peninsula, while the South's new president accused the North of pointless provocations in his first comments on their strained relations.

In a statement sent to the South, a North Korean general threatened that his country would take unspecified "military countermeasures" against its neighbor, the South Korean Defense Ministry said.

The North was responding to a Defense Ministry message Wednesday asking the communist North to stop trying to provoke the South, saying Seoul was ready for dialogue to promote peace.

The North's military was expected to ban South Korean officials from crossing the border for talks and other reasons, ministry spokesman Kim Hyung-ki told reporters, according to his office.

Kim said South Korea has decided not to respond again to the North as it has already conveyed its position.

North Korea has recently made a series of angry gestures, including test-firing missiles, since South Korean President Lee Myung-bak took office in February with pledges to get tough on the North and hold it accountable to its commitments to roll back its nuclear programs.

Lee said in a meeting with top military brass Thursday that the North's recent actions were "not desirable," according to South Korean pool reports.

Lee was personally targeted in a North Korean propaganda missive earlier this week that labeled him a "traitor" and warned that the South would face unspecified consequences for Lee's pro-U.S. policy.

The North has also threatened to turn the South to "ashes" in a pre-emptive strike, responding to remarks by South Korea's top military officer that Seoul could target suspected North Korean nuclear sites if there were signs of a pending atomic attack.

Lee said the officer's comments "were a natural answer" in response to lawmakers' questions at a parliamentary hearing, according to the pool reports.

He added that the North should refrain from "taking issue with remarks that don't have other meanings."

In the past week, North Korea has also expelled South Korean officials from a jointly run industrial zone and threatened to suspend reconciliation talks.

On Thursday, the North continued its bellicose rhetoric with warnings that Lee's policies may cause a "nuclear disaster" on the Korean peninsula.

"The reckless anti-North Korea policy by the U.S. and South Korea is fostering a grave situation that can lead to the breakout of a new war," the central committee of the Democratic Front for the Reunification of the Fatherland said in a statement carried by the North's Korean Central News Agency. The committee is affiliated with the North's ruling Workers' Party.

Lee, who has criticized his two liberal predecessors for giving unconditional aid to North Korea, is a strong advocate of improved ties with the United States to resolve the North's nuclear threat and revive his country's economy.

He called Thursday on North Korea to change its policy on South Korea, citing his government's push for "practical" talks that can be mutually beneficial to both Koreas.

"The North has recently fostered tension since the inauguration of the new government," Lee said. "The new government aims to have a dialogue with sincerity on inter-Korean issues. To do so, the North should also stay a little bit away from the pattern it has been taking so far."

Rising tension between the two Koreas comes as international efforts to rid the North of its nuclear weapons remain deadlocked over the North's pledge to declare all its nuclear programs for eventual dismantlement.

During a visit to Seoul this week, chief U.S. nuclear envoy Christopher Hill told reporters he was waiting for the North's next move in the next few days to resolve the impasse.