NORTH Korea says it won't agree to a "humiliating" dialogue with the United States and that talks are only possible if Washington abandons its "hostile" policy and nuclear threats.

"We do not oppose dialogue but cannot sit face-to-face at the humiliating dialogue table with the other party who is wielding a nuclear stick," a foreign ministry spokesman said in a statement issued on state media on Tuesday.

"As long as the US sticks to its hostile policy and nuclear blackmailing against (North Korea), sincere dialogue can be held only after (the North) prepares its nuclear deterrent fully to thwart a US threat of nuclear war."

The statement came a day after US Secretary of State John Kerry wrapped up a Northeast Asian tour aimed at defusing soaring military tensions on the Korean peninsula and getting China to help rein in a belligerent Pyongyang.

Kerry said in Tokyo that Washington was ready to talk to North Korea but that Pyongyang had to take "meaningful steps" to honor its international commitments.

"The United States remains open to authentic and credible negotiations on denuclearization, but the burden is on Pyongyang," he said.

The North's spokesman said recent overtures by senior US officials were a "cunning plot" to avoid responsibility for raising tensions on the Korean peninsula and were only aimed at removing North Korea's nuclear weapons.

State media said the Supreme Command of the Korean People's Army issued an ultimatum demanding an apology from South Korea for "hostile acts" and threatening that unspecified retaliatory actions would happen at any time.

The statement, relayed through the KCNA state media agency, came after a day of festivities in North Korea's capital that featured art performances, public dances and crowds thronging to giant bronze statues to pay homage to the late leader Kim Il Sung.

It comes as a a US military helicopter crashed near the North Korean border during a joint military exercise with South Korea. There were no reported casualties from the crash.

The renewed rhetoric was sparked by a protest in downtown Seoul, where effigies of Kim Il Sung and his son and successor, late leader Kim Jong Il, were burned. Such protests are not unusual in South Korea and this one likely gave the North a pretext to react negatively to calls for joining in dialogue with its neighbors than an actual cause for retaliation.

media_camera US Secretary of State John Kerry delivers remarks to US Foreign Service workers during a "meet and greet" visit to the US Embassy in Tokyo on April 15, 2013. Kerry, who wrapped up his East Asian tour, said on April 15 the US will talk with North Korea if it takes "meaningful steps" towards peace, as the world watched to see if Pyongyang will mark its founder's birthday with a missile launch. AFP PHOTO / POOL / Paul J. RICHARDS

The North's statement said it would refuse any offers of talks with the South until it apologised for the "monstrous criminal act." North Korea often denounces such protests, but rarely in the name of the Supreme Command, which is headed by Kim Il Sung's grandson and North Korea's new leader, Kim Jong Un.

"If the puppet authorities truly want dialogue and negotiations, they should apologize for all anti-DPRK hostile acts, big and small, and show the compatriots their will to stop all these acts in practice," the statement said, referring to North Korea's official name.

NORTH KOREA IN PERMANENT WAR

media_camera TOPSHOTS This picture taken on April 14, 2013 shows a woman North Korean soldier patrols along the bank of the Yalu River in the North Korean town of Sinuiju across from the Chinese city of Dandong. US Secretary of State John Kerry said he would be prepared to reach out to Pyongyang urging it back to negotiations, as he vowed Washington would protect Japan from North Korea's threats. CHINA OUT AFP PHOTO

South Korea's Defense Ministry said Tuesday it had received no such ultimatum officially, noting that there is no communications line between the two Koreas.

Pyongyang launched a rocket ahead of the last anniversary of Kim Il Sung's birth, which was the centennial, but the holiday this year has been much more low-key, with Pyongyang residents gathering in performance halls and plazas and taking advantage of subsidised treats, like shaved ice and peanuts, despite unseasonably cold weather.

The calm in Pyongyang has been a striking contrast to the steady flow of retaliatory threats North Korea has issued over ongoing military exercises between South Korea and the United States. Though the maneuvers, called Foal Eagle, are held regularly, North Korea was particularly angry over their inclusion this year of nuclear-capable B-2 stealth bombers and F-22 fighters.

media_camera In this April 15, 2013 image made from video, North Korean leader Kim Jong Un, center, accompanied by North Korean soldiers visits Kumsusan Palace of the Sun in Pyongyang, North Korea. North Koreans celebrated the birthday of their first leader Monday by dancing in plazas and snacking on peanuts, with little hint of the fiery language that has kept the international community fearful that a missile launch may be imminent. (AP Photo/KRT via AP Video) TV OUT, NORTH KOREA OUT

"The ultimatum is just North Korea's way of saying that it's not willing or ready to talk with the South," said Chang Yong-seok at the Institute for Peace and Unification Studies at Seoul National University.

"North Korea apparently wants to keep the cross-border relations tense for some time to come."

NORTH KOREA'S MISSILE POTENTIAL

media_camera People visit giant statues of the late North Korean leaders, Kim Il Sung, left, and his son Kim Jong Il, in Pyongyang, North Korea, Monday, April 15, 2013. Oblivious to international tensions over a possible North Korean missile launch, Pyongyang residents spilled into the streets Monday to celebrate a major national holiday, the birthday of their first leader, Kim Il Sung. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO LICENSING IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

The Tuesday ultimatum comes just after US Secretary of State John Kerry wrapped up a tour to coordinate Washington's response with Beijing, North Korea's most important ally, as well as with Seoul and Tokyo. Kerry said a missile test would be provocation that would further isolate the country and its impoverished people. He said Sunday that the US was "prepared to reach out," but that Pyongyang must first bring down tensions and honor previous agreements.

South Korean Defense Minister Kim Kwan-jin told a parliamentary committee Monday that North Korea still appeared poised to launch a missile from its east coast. North Korea, which conducted a nuclear test in February, has already been slapped with strengthened UN sanctions for violating Security Council resolutions barring the regime from nuclear and missile activity.

To further coordinate their response, South Korea's new president, Park Geun-hye, will meet with President Barack Obama on May 7 at the White House.

media_camera South Korean army soldier stand guard on Unification Bridge in Paju, South Korea, near the border village of Panmunjom, Tuesday, April 16, 2013. North Koreans danced in plazas and snacked on peanuts as part of holiday festivities while the Supreme Command led by North Korean leader Kim Jong Un offered more of the fiery language that has made the international community wary of an imminent missile launch or other provocation.(AP Photo/Ahn Young-joon)

GALLERY: KOREAN TENSIONS MOUNT

State Department spokesman Patrick Ventrell said Monday the United States is open to dialogue with North Korea but only if Pyongyang proves itself to be trustworthy.

"The burden remains on Pyongyang. They need to take meaningful steps to show that they'll honor their commitments," Ventrell told reporters in Washington.

"We need to see them be serious about denuclearization, indicate their seriousness, and start to reduce the threats and stop provocations."

North Korea has warned that the situation has grown so tense it cannot guarantee the safety of foreigners in the country and said embassies in Pyongyang should think about their evacuation plans. But British Foreign Secretary William Hague said Monday that although there is reason for concern over the "frenetic and bellicose" rhetoric, Britain believes there has been "no immediate increased risk or danger" to those living in or travelling to North Korea.

Pyongyang's media gave little indication of how high the tensions are.

media_camera South Korean protesters burn effigies of North Korean leader Kim Jong-Un, and late leaders Kim Jong Il and Kim Il Sung at an anti-North Korea protest on the birthday of Kim Il Sung in Seoul, South Korea. (AP Photo/Kin Cheung)

The front page of the Rodong Sinmun, the Workers' Party newspaper, on Tuesday featured photos of Kim Jong Un at a performance the night before of the Unhasu orchestra, along with his aunt, Kim Kyong Hui, and other top officials. North Korean media also reported that he watched volleyball and basketball games between Kim Il Sung University of Politics and Kim Il Sung Military University.

Starting from early Monday morning, residents dressed in their finest clothing began walking from all parts of Pyongyang to lay flowers and bow before the bronze statues of Kim and his son, late leader Kim Jong Il, as the mournful "Song of Gen. Kim Il Sung" played over and over. Similar statues of the Kims are located in every North Korean province.

media_camera Military personnel salute as civilians bow to giant statues of the late North Korean leaders, Kim Il Sung and his son Kim Jong Il, unseen, in Pyongyang, North Korea, Monday, April 15, 2013. Oblivious to international tensions over a possible North Korean missile launch, Pyongyang residents spilled into the streets Monday to celebrate a major national holiday, the birthday of their first leader, Kim Il Sung. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO LICENSING IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

media_camera North Korea's missiles

media_camera South Korean army soldiers conduct military exercise in Paju, South Korea, near the border village of Panmunjom, Tuesday, April 16, 2013. North Koreans danced in plazas and snacked on peanuts as part of holiday festivities while the Supreme Command led by North Korean leader Kim Jong Un offered more of the fiery language that has made the international community wary of an imminent missile launch or other provocation.(AP Photo/Ahn Young-joon)

media_camera This picture taken by North Korea's official Korean Central News Agency (KCNA) on April 15, 2013 shows North Korean people visiting the Kumsusan Palace, where late leaders Kim Il Sung and Kim Jong Il's bodies are enshrined in Pyongyang, to commemorate the 101st anniversary of the birth of Kim Il Sung. AFP PHOTO / KCNA via KNS THIS PICTURE WAS MADE AVAIALBLE BY A THIRD PARTY. AFP CAN NOT INDEPENDENTLY VERIFY THE AUTHENTICITY, LOCATION, DATE AND CONTENT OF THIS IMAGE. THIS PHOTO IS DISTRIBUTED EXACTLY AS RECEIVED BY AFP.

Originally published as N Korea rejects dialogue with US