May 29 (Bloomberg) -- North Korea today carried out its sixth launch of a short-range missile this week, the latest act of defiance in the face of international condemnation over its May 25 nuclear test.

U.S. Defense Secretary Robert Gates said today that the atomic test may present an opening for China to back a tougher response to North Korea from the international community.

The missile was launched off North Korea’s eastern coast at 6:10 p.m. local time, the South Korean Defense Ministry said in a faxed statement, confirming a report by Seoul-based Yonhap News. The ministry said it couldn’t verify a Yonhap report that the weapon is a new type of surface-to-air missile.

North Korea fired two short-range missiles within hours of this month’s nuclear test and three more the following day. The nuclear test was the communist nation’s second and most powerful in three years.

North Korea also shows signs it plans to fire a short-range missile from the western coast, Yonhap said later. The nation faces Japan to the east across the Sea of Japan and China to the west across the Yellow Sea.

North Korea said today the nuclear test was done in “self- defense,” and that it was prepared to take similar measures if the United Nations moves to impose more sanctions on the country. The U.S. and Japan want a statement from the UN Security Council that calls for cutting North Korea’s global financial ties and to forbid the regime from selling weapons to raise money, UN diplomats said.

Threat to Armistice

“Hostile” acts by the UN will nullify the 1953 armistice that ended the Korean War, an unidentified North Korean Foreign Ministry spokesman said in comments carried by the country’s official Korean Central News Agency. North Korea has already once this week declared the armistice null and void because South Korea joined a U.S.-led anti-weapons proliferation initiative.

China’s Foreign Ministry has said the country “resolutely opposes” North Korea’s nuclear test. China on May 25 agreed with the U.S., Japan and Russia to work toward a UN Security Council resolution censuring North Korea.

“Just based on what the Chinese government has said publicly, they’re clearly pretty unhappy,” Gates told reporters traveling with him to Singapore for an annual Asian security conference known as the Shangri-La Dialogue. “It is important for the Chinese to be part of any effort to try and deal with these issues.”

Any diplomatic response and economic sanctions should be coordinated among partner countries, Gates said, adding that he doesn’t foresee military action “unless they do something that requires it.”

Aim of Sanctions

Potential sanctions should be aimed at the regime without causing harm to the North Korean people, Gates said. North Korea’s actions don’t require any reinforcement of the U.S. military presence in South Korea, he said. There are 28,500 U.S. troops stationed in the country.

Gates arrived in Singapore today and then will head to the Philippines to reinforce President Barack Obama’s message that the new administration won’t waver in the long-held U.S. commitment to Asian security.

U.S. Secretary of State Hillary Clinton, who this week said North Korea must face consequences for its “belligerent and provocative behavior” will send deputy James Steinberg to China, South Korea, Japan and Russia to discuss the North Korean issue, department spokesman Ian Kelly said today.

Talks in Washington

South Korean Foreign Minister Yu Myung Hwan will visit Washington on June 5 to meet Clinton and discuss North Korea as well as President Lee Myung Bak’s U.S. summit with Obama slated for June 16, the ministry said.

South Korea reacted to North Korea’s provocation by joining the Proliferation Security Initiative, or PSI, set up to seize illegally transferred weapons of mass destruction. The North responded by saying it would retaliate militarily to any such move. Gates indicated he didn’t see an imminent threat.

“I don’t believe that anybody in the administration thinks that there is a crisis,” Gates said.

The events of the past week mark an escalation of tensions since last year, when North Korea refused to abide by what the U.S. said were verbal pledges to allow sufficient inspections to verify the extent of its nuclear activities. The breakdown in six-nation talks to end the atomic program followed reports that North Korean leader Kim Jong Il had suffered a stroke.

Maritime Warning

North Korea also raised the possibility of a maritime confrontation, saying it can’t guarantee the safety of ships passing through its western waters. The statement specified five islands controlled by the South that were the site of naval skirmishes in 1999 and 2002.

Chinese fishing boats are leaving the waters near the maritime border between North and South Korea, South Korean Defense Ministry spokesman Won Tae Jae said today. South Korea’s military is closely monitoring troop movements in North Korea for signs that Kim’s government has warned China of a possible skirmish in the area.

The actions have drawn international condemnation. The UN and the six-nation talks that also involve Japan, Russia, China and South Korea are still the best forum for resolving the issues, Gates said.

“I don’t want to put the burden entirely on China,” Gates said. “The reality is that while China has more influence probably than anybody else on North Korea, I believe that that influence has its limits.”

To contact the reporters on this story: Heejin Koo in Seoul at hjkoo@bloomberg.net; Viola Gienger in Washington at vgienger@bloomberg.net.

Last Updated: May 29, 2009 09:06 EDT