Reid is expected to fly to the United States early next week from England, where he was sorting his visa when the 2020 MLS season was suspended due to the COVID-19 pandemic. He should be available for the MLS is Back Tournament, which begins July 8 in Florida.
Like most loans, West Ham had the option to recall Reid. With the remainder of West Ham's season condensed over a short period of time as the Premier League resumed this week, a source said that SKC were worried manager David Moyes would recall Reid as part of an all-hands-on-deck approach to fight against relegation.
The loan agreement for Reid is through the end of the season and includes a purchase option for SKC.
Reid, 31, has dealt with several injuries over the past few years, stalling his career somewhat. He hasn't played made a competitive senior appearance since March 2018, but is a World Cup and Premier League veteran. He joined West Ham in 2010 and made 223 appearances with the club.
SKC are deep in central defense, as new signing Roberto Puncec partnered with captain Matt Besler through their first two matches this season. Peter Vermes can also call on Botond Barath, Andreu Fontas or Graham Smith.
Sporting KC have been drawn into Group D of the MLS is Back Tournament alongside Real Salt Lake, Colorado Rapids and Minnesota United. SKC got off to a flying start in 2020, winning both of their matches with a strong goal difference of +6.