Biden, who won’t take office until the end of January, has begun to build his own core team, according to the website of the Daily Star. Unlike trump, Biden uses experts in various fields rather than relatives and friends to build his own team, the report said. < / P > < p > a key role in the core team is the U.S. ambassador to the UK, and Biden, who will take office, may be making a very controversial choice. Biden is considering appointing former US President Barack Obama as US ambassador to the UK, according to a senior conservative party source. According to the report, this may put British Prime Minister Boris Johnson in a difficult situation. Because he has made “potentially insulting remarks” to Obama more than once.