North Korea Response: What Can The United States Do?

N Korea NuclearABC News Photo Illustration

President Obama's pledge to more aggressively pursue diplomatic solutions to world challenges is being put to the test by North Korea, a country that has long defied the United States and the international community, which tested its biggest nuclear bomb yet on Monday and fired short range missiles Tuesday off its east coast, according to local media reports.

"Our army and people are fully ready for battle... against any reckless U.S. attempt for a pre-emptive attack," North Korea's government said through the state-run KCNA news agency. "It is clear that nothing has changed in the U.S. hostile policy against DPRK (North Korea)... even under the new U.S. administration."

VIDEO: Susan Rice, U.S. ambassador to the U.N., addresses the administrations next move.Play

Monday night, senior administration officials sat in the White House's Situation room, debating late into the night about what steps the United States should take now.

U.S. ambassador to the United Nations, Susan Rice, said the rogue regime, which has for a long time been isolated from the international community -- as well as neighbors and U.S. allies South Korea and Japan -- will only face further condemnation.

"We have Russia and China that have stepped in and together we have increased the pressure," Rice said on "Good Morning America." "Together we're going to increase pressure and concerted efforts to try and prevent North Korea from pursuing arms."

VIDEO: The administration is working on an effective response to the rogue regime.Play

North Korea conducted an underground nuclear test, and three short-range missile on its east coast. Reports overnight said the country tested two more short-range missiles with a range of about 80 kilometers. On Tuesday or Wednesday, the country could test fire another missile off of its west coast.

Obama has long said that dialogue with U.S. foes is more effective than harsh words, but the tests this weekend indicated that at least so far words have meant nothing to Kim Jong-Il and his regime.

"North Korea's nuclear ballistic missile programs pose a great threat to the peace and security of the world and I strongly condemn their reckless action," President Obama said on Monday. "North Korea's actions endanger the people of Northeast Asia, they are a blatant violation of international law, and they contradict North Korea's own prior commitments."

He called on the international community to "take action in response," starting with action from the United Nations.

"We will work with our friends and our allies to stand up to this behavior and we will redouble our efforts toward a more robust international nonproliferation regime that all countries have responsibilities to meet," the president said.

Nuclear Standoff

Strong words from the UN Security Council last month warning against an April missile test apparently did not have a significant impact on North Korea beyond the ejection of U.S. scientists and UN weapons inspectors.

In fact, this weekend's tests are an act of defiance against that statement, Rice said, and North Korea could be testing whether it can intimidate the international community.

"They are trying to say, 'Until the Council backs down… we're going to pursue this,'" Rice suggested. "The message we [the UN] are sending is… 'We will not back down.'"

The UN Security Council convened an emergency meeting on Monday condemning the nuclear test and in a statement, the council said that it would immediately begin work on a resolution.

Russian Ambassador o the UN Churkin said "the members of the Security Council voiced their strong opposition to and condemnation of the nuclear test conducted by the Democratic People's Republic of North Korea." Churkin said the test constituted a "clear violation" of UN resolutions.

Even China, which is probably North Korea's only ally in the region, outwardly opposed the test and called on the country to resume talks.

Actions Toward North Korea

Some experts say stricter sanctions on the country could help deter North Korea's nuclear ambitions.

"The strongest thing that could come out of the UN is a round of sanctions on military equipment, nuclear-related equipment both on imports and exports," said Michael Levi, a senior fellow at the Council on Foreign Relations (CFR) and author of "On Nuclear Terrorism." "And also perhaps something targeted at financial instruments."

Others say targeting North Korean finances outside the country, especially if Russia and China cooperate, could also be an effective way to exert pressure.

Some experts say simply keeping his pledge of offering an olive branch could help Obama temper North Korea's high-stakes nuclear standoff with the west.

"I think the thing to do is to get a message to them from a person high enough in the administration so they will know it is a new stage in the relationship – a message saying we take you seriously, we want to talk," said former ambassador to South Korea under George H.W. Bush, Donald Gregg.

The size of the blast has yet to be determined and scientists will measure it by testing radioactive particles in the air. The Russian government initially estimated the size of Monday's blast at between 10 and 20 kilotons, within the range of the size of the nuclear bombs that the US dropped on Hiroshima (13 kilotons) and Nagaski (22 kilotons) to end World War II.

But the United States downplayed that claim with a senior administration official assessing its size as "a few kilotons."

Senior administration officials said North Korea only notified the State Department of its intention to conduct a nuclear test without a specific time frame only a day before it actually did it.

The reaction of the international community to North Korea's tests could also signal how the United States and UN would response to Iran, which, some say, is also seeking nuclear capability.

Rice said instead of emboldening Iran's regime, this event could actually teach them a lesson.

"What Iran would see, if it is watching this carefully, that further a country like North Korea strains from its obligations, from fulfilling its commitment… the more pressure, the more sanctions, the more isolations it will face," Rice said on "GMA." "And I think that sends exactly the right message to other countries that may be deciding how to proceed."