The White House continued to put pressure on China today to help stabilize relations between North and South Korea after yesterday's artillery attack, the heaviest attack by North Korea on the South since the Korean War.
Today, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, warned of destabilization in East Asia if North Korea acquires nuclear weapons or continues to provoke its neighbors. He said that the United States is working with the rest of South Korea's allies to ease tension between the two countries.
Mullen said China will play a pivotal role in ensuring that North Korea does not escalate its actions.
"The one country that has influence in Pyongyang is China, and so their leadership is absolutely critical," Mullen said in an appearance with his wife, Deborah, on "The View."
China is North Korea's only ally and main economic partner. Officials from the State Department said that China has a duty to tell Pyongyang that deliberate acts "specifically intended to inflame tensions in the region" are not acceptable.
Secretary of State Hillary Rodham Clinton is expected to discuss the attack by telephone with China's foreign minister.
Obama Condemns Attack
In an exclusive interview with Barbara Walters Tuesday, President Obama called on China to stand firm and "make clear to North Korea that there are a set of international rules that they need to abide by."
Obama reiterated the country's support of South Korea, calling the nation "a cornerstone of U.S. security in the Pacific region."
Watch more of Barbara Walters' interview with the Obamas tonight on "World News With Diane Sawyer" and Friday, Nov. 26 at 10 p.m. ET on "A Barbara Walters Special: A Thanksgiving Visit with President and Mrs. Obama"
Attack Linked to Succession of North's Leadership
U.S. officials believe the artillery attack on the island of Yeonpyeong that set homes on fire and killed at least two South Korean marines and civilians was an isolated incident. The Obama administration linked it to the recent succession of power in North Korea from Kim Jong Il to his son, Kim Jong Un.
Despite there being no information that North Korea will continue an extended military operation against South Korea, Adm. Mullen said the United States and the rest of South Korea's allies are still on alert.
"I think worrying is something we ought to stay with," Mullen said." "It's a worrisome leadership in North Korea. He [Kim Jong Il] is a very unpredictable guy, a very dangerous guy."
North Korea's Nuclear Arsenal
The Joint Chiefs of Staff chairman also warned of destabilization if North Korea continues to try to build a nuclear arsenal. Just days before the attack, North Korean revealed an upgraded and strengthened uranium enrichment plant to western scientists.
"The revelation last week of this uranium enrichment facility is a big deal. It actually was described as a very sophisticated modern facility," Mullen said. "If he [Kim Jong Il] continues on that path, him with nuclear weapons or his son is a very dangerous outcome for the long term and it will continue to destabilize a really important part of the world," Mullen said.
Today Kim Jong Un and Kim Jong Il toured a university and food factory, making no comment about the artillery attack.
In South Korea, the country remains at a high alert level, just below a state of all-out war. South Korean officials have promised "enormous retaliation" if further provoked.
Military Exercises With South Korea To Resume
A White House official told ABC's Jake Tapper that the United States is discussing a number of measures with its allies, including action at the United Nations Security Council and further sanctions, and more joint U.S.-South Korea military exercises, to demonstrate solidarity and support.
The United States currently has 28,000 troops in South Korea.
Late last night, it was announced that starting next week, Nov.28 through Dec. 1, the USS George Washington and four other Navy ships will participate in military exercises with South Korea. The exercises were planned before the shelling attack and will take place in the Yellow Sea, west of the Korean peninsula.
In a statement from the U.S. Navy's Seventh Fleet, the military exercises are described as a measure to show the United States' "commitment to regional stability through deterrence."
The scene of yesterday's attack has been at the center of dispute where the two Koreas fought bloody skirmishes in 1999, 2002, and most recently November 2009. But this is the first time since the end of the Korean War in 1953 that North Korea has fired on South Korea's civilian territory.
U.N. Secretary General Ban Ki Moon called the attack one of "gravest incidents since the end of the Korean War" and said he "is deeply concerned by the escalation of tension on the Korean peninsula."
ABC News' Joohee Cho, Jake Tapper, Martha Raddatz, Alexander Marquardt, Kirit Radia, Luis Martinez and The Associated Press contributed to this report.