The United States expects to elevate its diplomatic relations with former foe Vietnam to the top level as President Joe Biden travels to Hanoi in a week, in a move that may irk China and with unclear business implications. Fearful of the potential reaction from its much larger neighbour, Vietnam had initially expressed caution about the upgrade. That led the Biden administration to multiply efforts to persuade the southeast Asian nation, including through multiple visits of high-ranking members of the U.S. government in recent months. The unprecedented push has led Washington to expect to be elevated to the top tier…