As first reported by David Ornstein of The Atheltic, the Hammers are set to sign Phillips on loan with an option to buy at the end of the season.
He is due for medical tests on Wednesday, February 24th.
Phillips arrived at Manchester City from Leeds in 2022 but has failed to break into the first team, leaving his future in doubt.
The England international will be hoping to revitalise his career with a move to the London Stadium.
He played 234 times for Leeds before moving to Manchester, where he struggled under the demands of Pep Guardiola and has been limited to just 31 appearances in all competitions, scoring one goal.
The midfielder will be looking for a fresh start with West Ham, who are pushing for a European finish in the Premier League and are in the knockout stages of the Europa League.
The Hammers will be hoping Phillips can follow in the footsteps of successful summer signings James Ward-Prowse, Edson Alvarez and Mohammed Kudus, who have all contributed towards their rise up the league table.