Leaders from the United Nations and United States continued to push for tougher measures against the Democratic People's Republic of Korea after it conducted its third nuclear test on Tuesday.

UN Secretary-General Ban Ki-moon on Thursday described the test as a "direct challenge to the international community".

"I have repeatedly called on the leadership of Pyongyang to give up its pursuit of nuclear programs and to instead focus on building a better future for the country's people by addressing dire humanitarian and human rights situations," Ban said in Washington before meeting US Secretary of State John Kerry.

"I encouraged the Security Council to act with unity and to take appropriate measures as soon as possible," said Ban, a career diplomat from the Republic of Korea before assuming his current post.

Kerry, who was meeting Ban for the first time as secretary of state, called the DPRK's test an "enormous provocative act that warrants a strong, a swift, and a credible response from the global community".

"I want to echo the Security Council's statement that this test is a clear threat to peace and security in the world," Kerry said.

"In the days ahead, we are going to ramp up our coordination with the Six-Party partners, with the Security Council and other UN members, and other allies and partners in order to guarantee that we respond appropriately."

While voices for more and tougher sanctions get louder by the day, Charles Armstrong, a professor of history and director of Center for Korean Research at Columbia University, believes that negotiation is still a better way than sanctions to solve the long-standing crisis.

The DPRK has been under sanctions for 60 years since the Korean War. The UN imposed sanctions in 2006 after the first nuclear test. Since then, the country has carried out two nuclear tests and successfully launched a satellite. Armstrong said it is not realistic to expect new sanctions be any more effective than previous ones.

"The only realistic way forward, as difficult as it may be to imagine now, is to bring North Korea into negotiations with the US and other countries to resolve the nuclear issue," he said.

Scott Snyder, a senior fellow for Korean studies and director of the program on US-Korea policy at the Council on Foreign Relations, believes that sanctions alone will not work with the DPRK, but they may be effective in slowing or delaying its procurement of items from abroad that could be used to advance nuclear and missile programs.

"This is a limited objective that is only one part of the broader challenge of dissuading North Korea from flouting international norms. Other instruments must be used alongside sanctions to facilitate changes necessary for North Korea to join as part of the international community," he said, referring to more diplomatic efforts and improved cooperation among DPRK's neighbors.

Ted Galen Carpenter, senior fellow for defense and foreign policy studies at the Cato Institute, said cooperation between the US and China on this issue is needed to move things forward.

"There is probably no longer a realistic way to get the DPRK to roll back its nuclear program," Carpenter said.

"Instead, China and the US need to work together on a new strategy, especially on Washington's part, to bring a nuclear-armed DPRK into cooperative international arrangements. The sanctions strategy is simply not working, nor is there much prospect that it will ever work."

Richard Bush and Jonathan Pollack, two senior fellows at the Brookings Institution, wrote in the think tank's blog that while some will fault Washington, Tokyo and Seoul for not having engaged Pyongyang to head off the tests of recent months, there is little or no evidence that Kim Jong-un would have been any more responsive to engagement than his father.

The three countries will likely respond to the test by seeking to tighten sanctions. There is ample room to improve the implementation of existing measures, and new financial sanctions are available, according to the two pundits, who both previously served in the US government.

While saying the DPRK test has put new pressure on China, they believe it will probably have the greatest impact on the ROK's president-elect Park Geun-hye, who will be inaugurated on Feb 25.

Park campaigned against current President Lee Myung-bak on the premise that his stance on the DPRK has been too tough and one-sided, and she proposed a "trust-building" process with Pyongyang and a focus on areas of potential mutual benefit.

"Her initiative is now very unlikely to get off the ground," wrote Bush and Pollack.

As fresh sanctions loom, the DPRK's Korean Central News Agency announced on Thursday that if the US and its allies challenge the DPRK with strong measures on its underground nuclear test, it will react with stronger measures for self-defense. The DPRK has repeatedly said that its test was designed to bolster its defense due to the hostility of the US.

Meanwhile, environmental agencies in China reported on Thursday that no artificial radioactive nuclides had been detected in Northeast China, which borders the DPRK.

Contact the writers at chenweihua@chinadailyusa.com and yuweizhang@chinadailyusa.com