In move seen as a possible prelude to the launch of a long-range missile toward Hawaii over the July Fourth holiday, North Korea on Thursday fired a barrage of short-range missiles off its east coast. Pyongyang had earlier marked a large area of water off its east coast as a no-sail zone through July 10, citing military drills. Thursday's launches of four short-range missiles were believed to be the North's first military action in the designated zone. Yonhap news agency, citing an unnamed military official, reported that all four missiles flew about 100 kilometers and identified them as KN-01 missiles with a range of up to 100 miles 160 kilometers. Japanese Prime Minister Taro Aso denounced the launches as "provocative." South Korea's foreign minister, Yu Myung-hwan, said the firings are "not a good sign because they are demonstrating their military power." South Korean analysts were skeptical about the possibility of a long-range launch anytime soon. Koh Yu-hwan, a professor at Seoul's Dongguk University, said he expects the North will take more time to assess international reaction to its recent pledge to expand its nuclear program. Tensions over North Korea's actions come as its leader Kim Jong Il has reportedly been laying the groundwork to hand power over to one of his sons, and as two American journalists were imprisoned for illegal border crossing and hostile acts. Analysts predict the North will continue its provocative acts in an attempt to command world attention that can lead to economic benefits. "I think what North Korea will continue to do is ratchet up the tension," said Brad Glosserman, another analyst at the CSIS think tank. "It needs that attention to get the concessions from other countries ... as well as to demonstrate its strength to domestic constituencies." US President Barack Obama has vowed the US won't make the same mistake of rewarding North Korea's bad behavior, and his administration has been pressing China - a key North Korean ally - to enforce the new UN sanctions against Pyongyang. In an interview with The Associated Press Thursday, Obama said he was trying to "keep a door open" for North Korea to return to international nuclear disarmament talks, but the country must abandon its nuclear weapons programs before it can join the world community. Philip Goldberg, in charge of coordinating the implementation of sanctions against the North, told reporters in Beijing that he had "very good conversations" with Chinese officials Thursday, though did not give details of the talks. Firing a ballistic missile on Independence Day would be a challenge to Washington, which has been rallying international support for enforcement of UN sanctions imposed against Pyongyang following a May 25 nuclear test. North Korea is banned from testing ballistic missiles under UN resolutions. Japan's Chief Cabinet Secretary Takeo Kawamura said Thursday that a long-range missile launch this weekend was possible. "We cannot rule out the possibility," he said, citing Pyongyang's past behavior. In 2006, North Korea launched its most advanced Taepodong 2 missile while the US celebrated Independence Day, though the rocket fizzled shortly after takeoff and fell into the ocean. Pentagon spokesman Bryan Whitman said the United States remains concerned about North Korea's missile and nuclear programs but called Thursday's launches "not unexpected." Several US Defense Department officials said there is nothing to indicate that North Korea is ready to launch a long-range ballistic missile and there appears to be no immediate threat to the United States. The April 5 launch of a Taepodong-2 required 12 days of preparation on the launch pad, which was fully observable to US satellites. Short and medium-range missiles, however, can be launched with little notice. Missile defenses around Hawaii were beefed up following a mid-June report in a Japanese newspaper that the North might fire a long-range missile toward the islands in early July. The head of the US Northern Command, Gen. Victor E. "Gene" Renuart, said in an interview with the Washington Times this week that US missile defenses are prepared to knock down any incoming North Korean missile. "I think we ought to assume there might be one on the Fourth of July," he said, according to the paper. North Korea raised concern in late April when it explicitly threatened to test-fire an intercontinental ballistic missile and warned of a nuclear test. The regime followed through with the atomic blast in May, leaving the ICBM test as its next likely step.