WASHINGTON, Nov 18 (Reuters) - Outgoing U.S. President Donald Trump has made no plans to host a summit of the Group of Seven (G7) advanced economies after cancelling a June gathering because of the COVID-19 pandemic, three diplomatic sources said on Wednesday. The Republican president, who has refused to accept the victory of Democrat Joe Biden in the Nov. 3 election, has not made a final decision, but time is running out to plan a major summit before he hands over power on Jan. 20, said one of the diplomatic sources and a fourth source familiar with the matter.