She said sanctions alone cannot solve the North Korean nuclear issue because the purpose of them is not to end North Korea's nuclear program, but to sharpen the choice that North Korea has to make. "Sanctions don't stop people from their behaviors, but can bring them to the negotiating table," Sherman noted. 

In the near future, the North Korean leader may venture another nuclear test, Sherman also predicted. "I expect that Kim Jong-un will test the next president, although we have not had a nuclear test yet today given the Korean anniversary of the workers' party," she said, adding that "I suspect we will in the near future." 

North Korea's pursuit of nuclear weapons and its increasingly sophisticated missile system will be "the top challenge" facing the next U.S. administration, Sherman also noted, highlighting that the South Korea-U.S. alliance will be central to Clinton's Asia policy if she becomes president. 

"North Korea should be under no illusion about the strength of the U.S. commitment and determination to defend the Republic of Korea. America is prepared to do all that is necessary to fulfill its commitment to defend South Korea," Sherman asserted. "Secretary Clinton understands our alliance is central to addressing together this difficult challenge that is so consequential to South Korea and the world."

Sherman also defended the planned U.S. deployment of the Terminal High Altitude Area Defense system in South Korea as being innocuous to China, saying, "Deployment of THAAD is an agreement that has been made between the U.S. and ROK because it is to protect South Korea from North Korean missiles."

"It is not about China; it is about North Korea," she emphasized. 

As for continuing public protests over the deployment plan, she said, "I am confident that the people of South Korea and government will solve this deployment decision and I will leave that to the people of your country," according to Sherman. 

The former official also shed light on the importance of China's role in denuclearizing North Korea.

"They are crucial to making a difference where North Korea is concerned," she said. "We need to impress upon China ... that their security is at risk as well, and it is then in their interest to be a partner in this regard and apply the pressure necessary to get Kim Jong-un to understand the choice he has to make."

Later in a separate meeting with journalists, Sherman made it clear that the option of military action should be the last choice of the options in the toolbox for denuclearizing North Korea.

"There are things we can do short of that, which we are already doing," she said, citing joint military exercises between the allies and the forward deployment of strategic military assets on the peninsula.
 
"I think the military option should always be the last option -- it should always be the last resort because it is dangerous. It has unintended consequences and the risks to South Koreans in particular are great," she said. "I think there are many things we can do before we have to consider that." (Yonhap)