Rex Tillerson travels to China to discuss North Korea

US Secretary of State Rex Tillerson traveled to Beijing to pile pressure on China over the North Korean crisis. The US believes China can do a lot more to curb Pyongyang's nuclear ambitions.

US Secretary of State Rex Tillerson was scheduled to meet with Chinese President Xi Jinping and his Foreign Minister Wang Yi, on Saturday. It is the secretary of state's second visit in office to the world's second-largest economy.

US President Donald Trump, who will travel to Asia in November, has repeatedly urged China to exert more pressure on North Korea, one of its regional allies, to convince the Kim Jong Un regime to reverse its nuclear and missile programs.

Pyongyang has conducted six nuclear tests to date and 15 missile launches this year alone, which experts say demonstrates the regime has a viable nuclear capability.

China, North Korea's main trading partner, has backed UN sanctions on its ally. On Thursday, the Chinese government announced that North Korean companies must close their operations in China by January in line with the latest round of international penalties.

Ahead of Tillerson's Saturday trip, Susan Thornton, the acting US assistant secretary for East Asia, told US lawmakers that US-China cooperation over North Korea was increasing.

"We are working closely with China to execute this strategy and are clear-eyed in viewing the progress — growing, if uneven — that China has made on this front," she said.

"We have recently seen Chinese authorities take additional actions," Thornton added.

A delicate line

Trump has threatened to use military force against Pyongyang if the conflict accelerates.

"The United States has great strength and patience but if forced to defend itself or its allies, we will have no choice but to totally destroy North Korea," Trump said to the UN General Assembly last week.

In a display of military strength, US bombers and fighter escorts flew over North Korea last week. The planes flew to the farthest point north of the border between North and South Korea by any such US aircraft this century, the Pentagon said, adding that the mission showed "how seriously President Donald Trump takes North Korea's reckless behavior."

Read more: Donald Trump orders sweeping new travel ban, including N. Korea

Beijing appears to toe a delicate line between pressuring Pyongyang while at the same time avoiding any situation that would threaten the North Korean stability. China claims negotiations are the only workable solution to the crisis.

"China doesn't want the DPRK (Democratic People's Republic of Korea) to collapse because that would leave many uncertainties regarding its weapons, refugees and a US base at its doorstep," Eduardo Araral, vice dean of research at the Lee Kuan Yew School of Public Policy in Singapore, told DW.

Araral added that the US would not be able to handle North Korea without cooperation from China. "US-China ties are so intertwined that the US cannot continue hurting China, for example on trade, without hurting itself," he said.

Read more: Why China won't help US against North Korea

One of the major hurdles in preventing a united front from the US and China in dealing with the Kim regime is the uncertainty of the geopolitical outcome on the Korean Peninsula if the North were to collapse and be folded into the South.

US and Chinese interests do merge, however, in that both do not want a nuclear-ready North Korean military machine, and China especially does not want a nuclear war in its backyard.

Read more: North Korea nuclear 'blackmail' aimed at direct US talks

North Korea's history of taking US prisoners

'Crimes against the state'

In 2016, US student Otto Warmbier was arrested for allegedly stealing a propaganda poster as a "trophy." He was sentenced to 15 years of hard labor for "crimes against the state." In June 2017, he was returned by North Korea to the US in a coma and died a week later. What happened to him in captivity is a mystery. His death prompted a ban on US citizens traveling to North Korea.

North Korea's history of taking US prisoners

'Subversion and espionage'

Kim Dong Chul, a South Korea-born US citizen, was sentenced in 2015 to 10 years hard labor for "subversion and espionage" after North Korean officials said he received a USB stick containing nuclear-linked and military secrets from a South Korean source in North Korea. Chul was arrested while visiting the special economic zone of Rason. He remains imprisoned and his condition is unknown.

North Korea's history of taking US prisoners

'Trying to overthrow the regime'

In 2013, North Korea sentenced US citizen Kenneth Bae to 15 years hard labor for "crimes against the state." He was arrested while on a tour group in the port city of Rason. A North Korean court described Bae as a militant Christian evangelist. He was allowed to talk to the media once, and said he was forced to work eight hours a day and was in poor health. Bae was released in November 2014.

North Korea's history of taking US prisoners

'Rash behavior' and 'hostile acts'

In 2013, US citizen Matthew Miller was arrested when he arrived in Pyongyang and reportedly tore up his US passport, demanding asylum in North Korea. He was later sentenced to six years of hard labor on charges of espionage. The court said Miller had a "wild ambition" to experience prison life so that he could secretly investigate North Korea's human rights situation. He was released in 2014.

North Korea's history of taking US prisoners

'Criminal involved in killing civilians'

In 2013, Merrill Newman an 85-year-old Korean War US Army veteran, was detained for one month in North Korea. Arrested as he was departing, he was accused of "masterminding espionage and subversive activities." He was freed after he expressed "sincere repentance" and read a statement that said he was "guilty of a long list of indelible crimes against the DPRK government and Korean people."

North Korea's history of taking US prisoners

Freed by a diplomatic gesture

US journalists Euna Lee and Laura Ling were captured in 2009 after briefly entering North Korea to report on refugees. After a month in confinement, they were sentenced to 12 years hard labor for "illegal entry and "hostile acts." Two months later, after former US President Bill Clinton met with former North Korean leader Kim Jong Il in Pyongyang, the two women were pardoned and freed.