UNITED NATIONS (Reuters) - The U.N. Security Council on Tuesday unanimously condemned North Korea's December rocket launch and expanded existing U.N. sanctions thanks to a deal secured by the United States and Pyongyang's ally China.

Even though the resolution approved by the 15-nation council does not impose new sanctions on Pyongyang, diplomats said Beijing's support for it was a significant diplomatic blow to Pyongyang.

The resolution said the council "deplores the violations" by North Korea of its previous resolutions, which banned Pyongyang from conducting further ballistic missile and nuclear tests.

It also said the council "expresses its determination to take significant action in the event of a further DPRK (North Korean) launch or nuclear test."

The resolution added six North Korean entities, including Pyongyang's space agency, the Korean Committee for Space Technology, and the man heading it, Paek Chang-ho, to an already existing U.N. blacklist. It also added three other individuals to the blacklist.

The firms and individuals will face an international asset freeze, while Paek and the others blacklisted by Tuesday's resolution will also face a global travel ban.

U.S. Ambassador to the United Nations Susan Rice welcomed the resolution, describing it as introducing "new sanctions" against North Korea. Other diplomats, however, said on condition of anonymity that calling the measures in Tuesday's resolution "new sanctions" would be an exaggeration.

But they said that Beijing's decision to back the resolution would send a strong message to Pyongyang.

"It might not be much, but the Chinese move is significant," a council diplomat told Reuters. "The prospect of a (new) nuclear test might have been a game changer (for China)."

North Korea was already banned under Security Council resolutions from developing nuclear and missile technology. But it has been working steadily on its nuclear test site, possibly in preparation for a third nuclear test, satellite images show.

The United States had wanted to punish North Korea for the rocket launch with a Security Council resolution that imposed new sanctions against Pyongyang, but Beijing rejected that option.

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China is the North's only major diplomatic ally, although it agreed to U.N. sanctions against Pyongyang after North Korea's 2006 and 2009 nuclear tests.

December's successful long-range rocket launch, the first to put a satellite in orbit, was a coup for North Korea's young leader, Kim Jong-un.

North and South Korea are still technically at war because their 1950-53 conflict ended in a truce, not a treaty.

(Reporting By Louis Charbonneau; Editing by Mohammad Zargham and Philip Barbara)