Declassified Documents Show North Korea in the 1990’s Threatened to Restore Relations with Taiwan Over Chinese Leader’s Visit to South Korea
Here is an interesting bit of history which China clearly saw as empty threats from North Korea:

This photo, taken Nov. 14, 1995, shows then Chinese President Jiang Zemin (L) holding summit talks with South Korean President Kim Young-sam during his visit to Seoul. (Yonhap)
North Korea sharply reacted to growing relations between South Korea and China in the mid-1990s, even threatening to establish formal diplomatic relations with Taiwan in retaliation, declassified dossiers showed Tuesday.
Pyongyang’s objection came as China was arranging its then leader Jiang Zemin’s visit to Seoul for November 1995, three years after Beijing and Seoul established diplomatic ties in the post–Cold War era, a move that had angered the North, its traditional ally.
Diplomatic documents from 1995, released by the foreign ministry, revealed that the North had lashed out at China for drawing closer to the South in a June 1995 meeting of state think tank experts.
When the Chinese side voiced concerns over Pyongyang’s approach to Taiwan at the time, North Korean experts reacted sharply by asking, “Why shouldn’t North Korea develop relations with Taiwan when China and South Korea were engaging in high-level exchanges?” according to the dossiers.
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