According to reports, the 25-year-old former Brisbane Roar star is set to join the Premier League giants on a free transfer.
It is believed that Brattan, who has this week called up to the Australia squad for next month's World Cup qualifier against Jordan, has come to the attention of City via their sister club Melbourne City of the A-League.
Of the proposed move, Hull-born Brattan told the Courier-Mail: "I'll meet up with my agent when I get to England and he'll go over some things with me.
"City is a massive club and this will be a once in a lifetime chance."
During his career in the A-League, Brattan made over 80 appearances for the Roar, on the way to three titles and two minor premierships.