Iran has stationed defence staff in North Korea since late October apparently to strengthen cooperation in missile and nuclear development, Japan's Kyodo News agency reported on Sunday, citing a Western diplomatic source.

The report came as North Korea said on Saturday it would carry out its second rocket launch of the year between December 10 and 22, near the first anniversary of the death of young leader Kim Jong-un's father.

The Iranian mission, Kyodo said, is made up of four experts from Iran's Ministry of Defence and firms close to it. Citing the source, it said they were staying at a military facility 85 km (53 miles) from the North Korean border with China.

The two countries signed an agreement to cooperate in science and technology earlier this year.

North Korea has had close ties with Iran. Leaked US diplomatic cables from 2010 showed that US officials believe Iran has acquired ballistic missile parts from North Korea.

North Korea's state news agency announced the decision to launch another space satellite on Saturday, a day after Kim met a senior delegation from China's Communist Party in the North Korean capital of Pyongyang.

China, under new leadership, is North Korea's only major political backer and has continually urged peace on the Korean peninsula, where the North and South remain technically at war after an armistice, rather than a peace treaty, ended the 1950-53 conflict.

No comment on the planned launch was available from Beijing's foreign ministry.

In Washington, US State Department spokeswoman Victoria Nuland condemned the launch plan as a provocative threat to the Asia-Pacific region that would violate United Nations resolutions imposed on Pyongyang after past missile tests.

"A North Korean 'satellite' launch would be a highly provocative act that threatens peace and security in the region," she said in a written statement.

Pentagon spokesman George Little said, "North Korea must abide by its international obligations under UN Security Council resolutions that clearly articulate what it can and cannot do with respect to missile technologies."

Seoul's foreign ministry called the move a "grave provocation." Japan's Kyodo news agency said Prime Minister Yoshihiko Noda had ordered ministries to be on alert for the launch.

"North Korea wants to tell China that it is an independent state by staging the rocket launch and it wants to see if the United States will drop its hostile policies," said Chang Yong-seok, a senior researcher at the Institute for Peace Affairs at Seoul National University.

North Korea is banned from conducting missile or nuclear-related activities under UN resolutions imposed after earlier nuclear and missile tests. The country says its rockets are used to put satellites into orbit for peaceful purposes, but that assertion is not widely accepted outside of Pyongyang.

Washington and Seoul believe that the impoverished North is testing long-range missile technology with the aim of developing an intercontinental ballistic missile capable of carrying a nuclear warhead.

Pyongyang's threats are aimed, in part, at winning concessions and aid from Washington, analysts say.

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The failed April rocket launch took place to celebrate the 100th anniversary of the birth of North Korea founder Kim Il Sung and the latest test will take place close to the December 17 date of the death of former leader Kim Jong-il.

It will also come as South Korea gears up for a December 19 presidential election in a vote that pits a supporter of closer engagement with Pyongyang against the daughter of South Korean dictator Park Chung-hee.

The April test was condemned by the United Nations, although taking action against the North is hard as China refuses to endorse further sanctions against Pyongyang.

North Korea is already one of the most heavily sanctioned states on earth thanks to its nuclear programme.

Pyongyang has few tools to pressure the outside world to take it seriously due to its diplomatic isolation and its puny economy.

The state that Kim Jong-un inherited last December after the death of his father boasts a 1.2 million-member military, but its population of 23 million, many malnourished, supports an economy worth just $40 billion annually in purchasing power parity terms, according to the US Central Intelligence Agency.

"The North's calculation may be that they have little to lose by going ahead with it at this point," said Baek Seung-joo of the Korea Institute for Defense Analyses in Seoul.

Baek said the test planned for December would likely be no more successful in launching a satellite than the April one that crashed into the sea between China and North Korea after flying just 120 km (75 miles).

"Kim Jong-un may be taking a big gamble trying to come back from the humiliating failure in April and in the process trying to raise the morale for the military," Baek said.

North Korea's space agency said on Saturday that it had worked on "improving the reliability and precision of the satellite and carrier rocket" since April's launch. – Reuters