China's President Xi Jinping hailed an "invincible friendship" with Pyongyang as he arrived in North Korea Monday, his first trip abroad this year after hosting back-to-back summits in Beijing. China, Washington's chief geopolitical rival, has been North Korea's main trading partner by far for decades and a key source of diplomatic and economic support for the country hit by multiple international sanctions. Military officers lined a red carpet as an Air China plane carrying Xi arrived for his first visit since 2019, video from Xinhua showed.