Updated at 6:50 p.m. on November 23.
Now that North Korea's military assault on a South Korean island has stopped, Washington is reacting to what could escalate into a foreign policy crisis for Barack Obama.
In a senior national security team meeting Tuesday, the president said South Korea has the "unshakeable support of the United States," according to a White House release. Earlier in the day, press secretary Robert Gibbs condemned the attacks aboard Air Force One. "It’s an outrageous act. The President thinks that North Korea is not living up to their obligations and they ought to live up to the obligations that are signed in the armistice agreement and international law."
At the Pentagon, a spokesman noted that this attack followed one earlier this year on a South Korean naval vessel. "We take this very seriously, just as we took the sinking of the Cheonan earlier this year very seriously, in which the North murdered some  South Korean sailors," Pentagon Press Spokesman Geoff Morrell told MSNBC.
On Tuesday afternoon, as the president was traveling, the National Security Council met to discuss the situation on the Korean peninsula. National Security Adviser Tom Donilon chaired the meeting. Also present: The commander of U.S. forces in Korea, General Walter Sharp, as well as the commander of all U.S. assets in the Pacific, Adm. Frank Willard, participated via video conference. Secretary of Defense Robert Gates and Secretary of State Hillary Clinton attended in person. The president was later briefed on the situation by Donilon, Secretaries Clinton and Gates, Ambassador Susan Rice, Admiral Mike Mullen, and General Walter Sharp, Commander of U.S. Forces Korea, according to the White House.
The administration's criticism of North Korea was seconded in statements by both Democrats and Republicans in Congress, a rare display of bipartisanship that comes just weeks after a rancorous midterm election that left Republicans in control of the House of Representatives.
The incoming Speaker of the House, John Boehner, R-Ohio, said: "North Korea is an unstable aggressive regime and I join the president in condemning its hostile action today."
"As the people of the Republic of Korea question what new belligerent action may come from the North, they should not have any question that the people and forces of the United States stand ready as a devoted ally committed to the defense of their nation," Senate Minority Leader Mitch McConnell, the Senate's top Republican, said in a statement. "I join the president in his strong condemnation of what is sadly just the latest in a long string of hostile actions. North Korea's neighbors should unite in condemning this attack."
House Armed Services Committee Chairman Ike Skelton, a Democrat, called the artillery attacks "reprehensible" and said it was "in direct violation of the Armistice Agreement."
"The North Korean regime is more dangerous than most people realize. I join the administration in strongly condemning North Korea for its artillery attack against South Korea," Skelton said in a statement.
Sen. Dick Lugar, R-Ind., the ranking member on the Senate Foreign Relations Committee, urged the administration to focus on China, a country whose tacit acquiescence to North Korea's actions had been "emboldened."
The question of how to tame North Korea's aggressive impulses has been ongoing and the latest salvo from the North only complicates matters. At issues is whether the U.S. should engage in direct talks with the North Koreans, as the Pyongyang regime has long favored, or to pursue multilateral discussions as George W. Bush's White House pursued and as the Obama administration has continued.
But in an interview with ABC's Good Morning America, former U.S. ambassador to South Korea Donald Gregg who served in Seoul during the presidency of George H.W. Bush, advised the U.S. to engage North Korea in direct negotiations. The Obama White House and the previous administration have pursued multilateral talks with regional allies China, Russia and Japan in the believe that they'll be more productive because they have closer ties to the isolated regime in Pyongyang and thus more leverage to get North Korea to abandon its nuclear program. The "Hermit Kingdom" as its sometimes called has tested two nuclear devices, one in 2003 and one in 2009.
The attack on the island of Yeonpyeong comes just days after North Korea was revealed to have an advanced uranium enrichment facility that could advance Pyongyang's nuclear ambitions. The existence of the facility caught American officials by surprise.
American nuclear scientist Siegfried Hecker, the Stanford University professor who told the White House last week that he was shown the secret enrichment facility on a recent trip to North Korea, is scheduled to be back at the White House today to meet with Gary Samore, the White House Coordinator for WMD Counter-Terrorism and Arms Control, according to a knowledgeable White House official.
The facility is more significant for its sophistication than its size or potential output, the administration official said. What may be of greater concern is the suspicion that the North Koreans have more facilities than U.S. intelligence officials are unaware of, the official said.
On Monday, State Department spokesman P.J. Crowley told reporters the administration is studying the evidence a group of visiting American scientists used to conclude the North was building the enrichment facility, which presumably could be used to produce fuel for nuclear weapons.
"We will not be drawn into rewarding North Korea for bad behavior," he said. "They frequently anticipate doing something outrageous or provocative and forcing us to jump through hoops as a result. We're not going to buy into this cycle."
As for the president, he was awakened by this latest provocation at 3:55 a.m. when National Security Adviser Tom Donilon updated the president on the situation. Obama received further updates during his daily intelligence briefing Tuesday, ahead of his visit to Indiana to highlight economic issues.
Earlier this month, during a speech to U.S. troops stationed in South Korea, President Obama said: "Pyongyang should not be mistaken: The United States will never waver in our commitment to the security of the Republic of Korea. We will not waver."
While the attack on the South Korean island of Yeonpyeong was hardly the first North Korean act of aggression in recent years, it represented an escalation, says Sung-Yoon Lee, professor of East Asian Relations at Tufts University’s Fletcher School of Law and Diplomacy, because it was an attack on South Korean civilians on land. Recent attacks, such as March's sinking of a South Korean naval vessel, were at sea or on military personnel.
Video footage from the attack is below:
Aamer Madhani and Marc Ambinder, Sara Sorcher and The Associated Press contributed. contributed to this article.
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