He coached Real Salt Lake, New York City FC and Orlando City in MLS and was recently hired as a technical adviser to MLS expansion team
Inter Miami, a position he will maintain.
Kreis, who attended Duke University and starred at the Dallas Burn in the early days of MLS, spent seven seasons as the head coach at Real Salt Lake, winning MLS Cup in 2009, finishing second in the league in 2013 and taking RSL to the Concacaf Champions League final in 2011.
But he failed to replicate that success with Orlando City and New York City FC, where he left after its first season, having accumulated an 10-17-7 record. He joined Orlando City in July 2016, halfway through its second season, and left 15 games into the 2018 season. His record with the Lions was 21-29-14 in MLS play.
Kreis, who made 14 appearances with the USA, worked as a guest assistant coach in the men's national team's 2016 January Camp. Three of the caps came when he played with Earnie Stewart, the U.S. men's national team general manager, in 2000. Stewart said Kreis' background stood out and made him the best candidate to lead the U-23s.
"The U-23s are a significant part of our program, and Jason is an experienced head coach with significant success both in league and Concacaf competitions," said Stewart. "His knowledge of the player pool is impressive, and we are confident in his ability to implement the style of play we are building with the senior MNT and throughout our national teams."
The USA has failed to qualify for the last two Olympics -- and three out of the last four -- in men's soccer but has the deepest pool of U-23 players (players born in 1997 or later) it has ever assembled.
Four players with the senior national team in Florida are eligible for the 2020 Olympics as U-23 players: Tyler Adams, Jonathan Lewis, Weston McKennie and Christian Pulisic.
The group in Spain includes eight players who have been capped at the senior national team level, including Tim Weah and Josh Sargent, who played eight and six games, respectively, for the USA in 2018.
Djordje Mihailovic started both games at the end of the January camp and scored the first goal in new national team coach Gregg Berhalter's first game against Panama in January. Jeremy Ebobisse also started against Panama.
With five MLS games this weekend, some U-23 players are missing because of club commitments. Unlike the senior national team, clubs are under no obligation to release players for age-group teams.
The U.S. U-20s, who are preparing for the 2019 Under-20 World Cup in Poland, are also training at the Pinatar Arena. Players from the U-20s could also contend for spots on the U-23s.
No date has been set for Olympic qualifying in Concacaf, which will send two teams to the 16-team Olympic men's soccer tournament.
U.S. U-23 Roster:
Jonathan Klinsmann (Hertha Berlin/GER)
JT Marcinkowski (San Jose Earthquakes)
Julian Araujo (LA Galaxy)
Cameron Carter-Vickers (Swansea City/WAL)
Marco Farfan (Portland Timbers)
Jack Maher (Indiana Univ.)
Matthew Olosunde (Manchester United U23)
Donovan Pines (D.C. United)
Lucas Pos (Lausanne/SUI)
Antonee Robinson (Wigan Athletic/ENG)
Miles Robinson (Atlanta United)
Derrick Jones (Philadelphia Union)
Cameron Lindley (Orlando City)
Djordje Mihailovic (Chicago Fire)
Keaton Parks (New York City FC)
Eryk Williamson (Portland Timbers)
Jackson Yueill (San Jose Earthquakes)
Jeremy Ebobisse (Portland Timbers)
Josh Perez (LAFC)
Emmanuel Sabbi (Hobro/DEN)
Josh Sargent (Werder Bremen/GER)
Tim Weah (Celtic/SCO)
Haji Wright (Schalke/GER)