The 23-year-old will join City in July 2019 on a four-year deal for about £7m and will stay with the Crew for the first part of the MLS season, which starts in March.

Steffen is the United States number one and has six international caps.

City described Steffen as "one of the outstanding talents in America".

Crew said the transfer fee is the largest in their history and the most ever for an MLS goalkeeper in the league's 23-year history.

Steffen was voted the MLS Goalkeeper of the Year in 2018 after keeping 10 clean sheets.

"This is a historic transaction for the club and a special moment for Zack Steffen that we are immensely proud of," said Crew interim general manager Pat Onstad.

Steffen said the move was a "special moment" for him.