A North Korean all-female pop group canceled their Beijing concert last week when Chinese authorities objected to "anti-American" lyrics in the show, a source with ties to North Korea and China told Reuters on Friday.

The Moranbong Band was visiting China along with North Korea's State Merited Chorus and was due to perform at Beijing's National Centre for the Performing Arts on Dec. 12.

Chinese censors did not approve of a line which referred to the United States an "ambitious wolf", and lyrics which glorified the 1950-53 Korean War, according to the source.

"China did not ask that the lyrics be changed but it did not pass screening by censors," said the source, who declined to be identified due to the sensitivity of the subject.

"China was of the view that the lyrics would unnecessarily provoke the U.S.".

China has tried to act as an honest broker between the United States and North Korea and has repeatedly attempted to get the rivals to cool their rhetoric as it seeks to promote harmony in the region.

The Moranbong Band is North Korean leader Kim Jong Un's pet project as he tries to put his personal stamp on North Korean arts, and the short haircuts of the group's young women members are trend-setting in the capital, Pyongyang.

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The ensemble, whose members were reportedly handpicked by Kim, was formed in 2012, and the China show was to be their first overseas.

China's official Xinhua news agency has said the performance could not be staged because of "communication issues at the working level".

Asked repeatedly about the reasons for the cancellation at a daily briefing on Monday, a Chinese Foreign Ministry spokesman said he had nothing to add to the brief Xinhua story.

Asked about what the source said, the ministry's news division referred Reuters to the answer given on Monday.

'CONSULTED KIM'

China and North Korea were allies in the Korean War against a U.S.-led coalition and South Korea and some of the people invited to the concert were Chinese veterans of that war.

The North Koreans considered the Chinese officials invited to the event to be too low-ranking, the source added.

After the censor disapproved of the lyrics, the North Korean side protested, refused to change them and returned home after directly consulting North Korean leader Kim, the source said.

China invited the group to thank North Korea for hosting senior Chinese official Liu Yunshan at a military parade marking the 70th anniversary of the ruling Workers' Party in Pyongyang, the source said.

Chinese authorities paid for plane tickets and accommodation for the band.

There has been no word from North Korea on the canceled show. The visit was seen as an indication of improving relations between China and its isolated neighbor.

China is North Korea's main economic and diplomatic backer, but was infuriated in 2013 when Kim ordered the country's third nuclear test.

Several subsequent rounds of saber rattling by North Korea towards South Korea and the United States have also tested China's patience.