The two leaders have spoken five times during Biden's presidency and previously discussed a face-to-face meeting during a two-hour call in late July.The senior Biden administration official declined to elaborate on Covid-19 mitigation measures for the meeting, adding that health protocols were still being worked out by advance teams.They spoke about it extensively in March in their video call and then they spoke about it again in July, so it's part of an ongoing conversation between the two of them," the person added.Weeks before the Kremlin's full-scale invasion of Ukraine, Putin traveled to Beijing to meet with Xi and later issued a memorandum expressing a "no limits" relationship between their nations.The official, who spoke to reporters on the condition of anonymity, said Biden's national security advisor, Jake Sullivan, conveyed to China's top diplomat, Yang Jiechi, that the U.S. is concerned Beijing may attempt to help Russia blunt global sanctions."