By Jonathan Landay KHERSON, Ukraine (Reuters) -Kyiv welcomed reported Chinese comments criticising threats to use nuclear weapons as G20 leaders met in Indonesia on Tuesday, with Russia’s invasion of Ukraine in the spotlight. U.S. President Joe Biden and Chinese President Xi Jinping “underscored their opposition to the use or threat of use of nuclear weapons in Ukraine,” the White House said in a readout of a meeting in Indonesia between the two leaders on the eve of the summit. A readout of the Biden-Xi meeting on China’s foreign ministry website made no use of the word “nuclear” but said: “C…