North Korean leader Kim Jong Un is hugged by children during his visit to Samjiyon County in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang. Reuters/KCNA KCNA North Korea’s missile and nuclear technology might reach a tipping point if Washington and Pyongyang refuse to negotiate, a senior Chinese diplomat has warned.

In an analysis piece published on Sunday by US think tank the Brookings Institution, Fu Ying, chairwoman of the National People’s Congress’ Foreign Affairs Committee, said it was unrealistic to expect the regime of North Korean leader Kim Jong-un to succumb to pressure of sanctions or collapse.

“Sanctions may exert huge pressure, but the country can hold up and will not give up nuclear development because of them,” wrote Fu, who is also a former deputy foreign minister.

“It is not hard to see that this situation could make the issue drag on into a spiral of intensified sanctions and continued nuclear testing until [North] Korean nuclear and missile technologies reach a tipping point.”

She said that once that point was reached, the countries opposing Pyongyang’s possession of nuclear weapons would be “faced with the hard choice of taking extreme action with unknown consequences, or tolerating it”.

Fu also said it was unrealistic for the United States and South Korea to hope that the Kim regime would collapse from tightening its economic lifelines. “The reality is that the [North] Korean economy has already passed through its most difficult time. Kim Jong-un ... has stabilised the domestic situation,” she wrote.

U.S. President Donald Trump and China's President Xi Jinping chat as they walk along the front patio of the Mar-a-Lago estate after a bilateral meeting in Palm Beach, Florida, U.S., April 7, 2017. REUTERS/Carlos Barria Fu’s views reflect Beijing’s official line and her article comes as the US has stepped up its threats of a military response. But US President Donald Trump has also said he is willing to hold talks with Kim.

Fu said the only option was to return to the negotiating table but discussions could tougher than when representatives from the various players in the crisis first sat down for “six-party” talks in 2003.

“The ups, downs and many setbacks throughout multilateral negotiations have undermined the parties’ confidence in dialogue,” she wrote.

“If talks are resumed, whether all parties can accept such a reality and whether they can restart negotiations without preconditions remains an open question.”

She also repeated Beijing’s call for a “double suspension” – that Pyongyang suspend its nuclear and missile tests in exchange for a halt of large scale US-South Korean military exercises.

Fu said China did not have leverage over North Korea because Pyongyang’s security concerns in the face of US military threats had not been addressed.

Trump said on Monday that he would consider meeting Kim “under the right circumstances”.

Lu Chao, from the Liaoning Academy of Social Sciences, said Trump’s offer could be “positive” to the Korean crisis.

“As Fu Ying said, the key has never been owned by China,” Lu said. “The problem can only be solved by the two sides [the US and North Korea].

“I don’t think Kim would really want to wage a war with the US.”