Japan on Friday readied its missile defense systems to shoot down a North Korean rocket if it threatens the country, as the U.N. chief warned that next month's launch could jeopardize food aid.

The nuclear-armed North has announced it will launch a rocket in mid-April to put a satellite into orbit, a move that the United States, South Korea and other nations see as a pretext for a long-range missile test banned by the U.N.

The U.N. atomic agency IAEA has begun consultations with North Korea over a possible visit to the country by its inspectors to monitor its nuclear activities, a spokeswoman said Thursday.

"I can confirm that the IAEA has started consultations with the DPRK (North Korea) about its invitation," Gill Tudor, spokeswoman for the International Atomic Energy Agency, told Agencce France Presse by phone.

A U.S. military F-16 jet crashed in southern South Korea Wednesday during a training mission but its pilot ejected to safety, US authorities said.

The plane crashed into a rice paddy around noon (0300 GMT) near a U.S. air base in the western port city of Gunsan, the U.S. military said in a statement.

North Korea has invited U.N. inspectors to monitor a nuclear freeze deal with the United States, insisting the pact remains in force despite its shock announcement of a planned satellite launch.

Next month's scheduled launch, which would defy a United Nations ban, has sparked widespread complaints that the communist state is testing long-range missile technology which could one day deliver a nuclear warhead.

North Korea said Saturday it would invite foreign experts and journalists to observe a satellite launch which the United States and other countries see as a disguised missile test.

The Korean Committee for Space Technology "will invite experienced foreign experts on space science and technology and journalists" to visit the launch site and other places to observe the blast-off next month, the official news agency said.

North Korea announced Friday it would launch a rocket carrying a satellite next month, just 16 days after agreeing to suspend long-range missile tests in return for massive U.S. food aid.

The United States, Japan, and South Korea condemned the plan and said it would breach a United Nations ban imposed after previous launches.

A scuffle broke out Monday in the U.N. Human Rights Council and a man was detained by security after a North Korean diplomat said a critical report by an independent expert had been fabricated.

North Korea said it "roundly rejects this useless interpretation" which it said was "fabricated by hostile elements" and it called on the council not to renew the mandate of the special rapporteur on human rights Marzuki Darusman.

South Korean troops mounted a live-fire exercise near the tense border with the North on Thursday amid high tensions and in the face of Pyongyang threatening retaliatory strikes.

The one-hour exercise in Pocheon, the first of its kind this year near the land border, was a regular drill involving about 170 tanks, self-propelled howitzers, helicopters and four warplanes, a Defense Ministry spokesman told Agence France Presse.

North Korea Friday renewed threats to launch a "sacred war" against South Korea, indicating cross-border ties will remain icy despite Pyongyang's surprise nuclear deal with Seoul's close ally Washington.

The North's agreement to freeze some nuclear and missile activities in return for massive U.S. food aid has raised cautious hopes of eased tensions under its new young leader Kim Jong-Un.

North Korea's new leaders, hungry for food aid ahead of a landmark anniversary, have bought time in a deal with Washington but show no sign of actually renouncing their nuclear bargaining chip, experts say.

Under the deal announced Wednesday, the communist state now led by the young and untested Kim Jong-Un agreed to suspend nuclear and long-range missile tests, and its uranium enrichment program.