SEOUL – Four years after taking power, North Korea’s supreme leader, Kim Jong-Un, is solidifying control within the reclusive communist state and international sanctions meant to punish his regime have made little impact because of sharply increasing Chinese aid.

Beijing’s aid to Pyongyang more than doubled from $2.68 billion in 2009 to nearly $6.96 billion in 2014, undermining sanctions imposed by the United States and other nations in response to nuclear and missile tests and other military provocations, according to South Korean government officials.

"The Chinese provide for 90 percent of the North Korean economy despite sanctions imposed since the 2009 nuclear test," said a senior official who specializes in North Korean affairs. "Trade has more than doubled between 2009 and 2014."

The official urged the United States to pressure China into curbing support for North Korea, and to seek additional sanctions through Congress.

"Despite being seemingly stable from the outside, many factors indicate growing internal instability and signs of disunity," the official said. "Also there is growing discontent within the overall population."

Intelligence analysis of North Korea also indicates Pyongyang may carry out a nuclear test or long-range missile test that will be calculated to influence foreign policies toward the country, the officials said.

Kim Jong-Un, who took power after the death of his father Kim Jong-Il in 2011, has been mobilizing the entire country for future military action following a purge of potential rivals, notably his uncle Jang Sung-Taek.

There are increasing signs of instability within the upper levels of the communist dictatorship under the personality cult of the 32-year-old Kim.

"As a result of the purges of officials like Jang Sung-Taek, there is growing distrust between Kim Jong-Un and officials within the regime," said the senior official.

Jang, Kim’s uncle and a powerful figure within the North Korean regime who maintained close ties with China, was executed in December 2013 under charges of being a "counter-revolutionary." Officials here said that the execution was part of an effort to consolidate power by Kim that also has included replacing several key generals with those regarded as more loyal.

An Internet report in China recently disclosed that Jang had urged Chinese leaders to support Kim’s brother, Kim Jong-Nam, rather than Kim Jong-Un. That appeal was said to be transmitted to Kim Jong-Un by ousted Chinese security chief and Politburo leader Zhou Yongkang.

South Korean officials said the Kim regime has initiated a series of economic reforms that appear to be similar the economic reforms launched in China in the 1980s.

The economic reforms have resulted in approximately 1 percent economic growth since Kim’s succession.

The economic reforms include a farming reorganization plan that provides farmers with plots of land and a new policy of allowing grain exchanges in barter arrangements.

The new system, called "Pojoen," also involves allowing businesses more autonomy from government control, and emphasizes the sale of products.

"Overall North Korea seems to be following the opening process in China," the official said. "But the reforms will only have little effect because of the continued adherence to the planned economy [in North Korea]."

Pyongyang also is seeking to attract foreign investment and has set up 19 economic development zones around the country.

In military affairs, North Korea has been taking steps to reinforce the combat readiness of its troops.

"Kim Jong Un ordered that 2015 is the ‘Year to Make Glorious Achievement in Preparation for War,’" the senior South Korean official said.

North Korean military exercises over the winter sought to better simulate wartime fighting conditions and involved rehearsals of "surprise attack operations," the senior official said.

Recent military activities have included missile flight tests of a new sea-based anti-ship missile with a range of around 87 miles. Other recent missile tests included short-range ballistic missiles, Silkworm short-to-ship missiles, and SA-3 surface-to-air missiles. Long-range multiple-rocket launchers also were tested.

Regarding North Korean cyberattacks, the officials aid Pyongyang is expected to use its growing cyber warfare capabilities for criminal activities designed to raise money for the regime.

"There is a high possibility of North Korea doing that," the official said.

On North Korea’s development of a submarine-launched ballistic missile, the official said Pyongyang conducted what appeared to be the first underwater ejection test of a submarine-launched missile. "We do not know the results," the official said.

South Korea expects that North Korea is continuing development of submarine launched missiles (SLBMs) and will continuing testing the new missile the Pentagon has designated as the KN-11.

The SLBM test was first reported by the Free Beacon Feb. 18.

The submarine missile program is believed to be the result of North Korea obtaining older Golf-class Russian missile submarines in the 1990s.

The SLBM is expected to be a new type of nuclear-tipped North Korean missile.

Pyongyang currently has ground-based Nodong medium-range missiles and the Taepodong long-range ballistic missile.

North Korea has said it has developed a small nuclear warhead capable of being fired on the last stage of a missile.

"At this point there is nothing to confirm that they’ve done that," the official said, adding that the North will need to build a warhead that is 60 centimeters, or about 2 feet in diameter, for the missile warhead.

The key to influencing Pyongyang, according to the official, will be pressuring China to limit trade and assistance to the rogue state.

"What we need to do is reduce the trade between China and North Korea," the official said, adding that the U.S. Congress could help by imposing additional sanctions.

Additionally, a referral of Kim Jong-Un to the International Criminal Court for crimes against humanity, based on the U.N. Commission of Inquiry report, would add to pressure on the regime.

South Korea is currently working to produce the collapse of the North Korean government through pressuring Pyongyang on its human rights abuses as well as by trying to penetrate the North Korean system with information that will inform its people about the outside world.

One positive sign is the dramatic increase in mobile phone use in North Korea. An estimated 2 million people who are using mobile phones, the senior official said.

"We expect the use and distribution of mobile phones inside North Korea to continue," the official said.

The growing use of mobile phones is expected to increase the flow of information into North Korea.

"There is growing, hidden discontent among the elite," the official said. "If they become aware of the outside world, people in the economic and business sector, and young people, are motivated to seek change," the official said.

While China’s communist government is clearly unwilling to overthrow the government in Pyongyang, relations between the two countries are strained. The heavy reliance on China "is uncomfortable for North Korea," the official said.

A key indicator of the condition of the relationship will be a possible visit to Moscow by Kim Jong-Un this spring.