Siverio was part of the Cuban national team that travelled to Iowa for an exhibition game against a collegiate all-star team from the U.S. But he apparently left the delegation at some point after it arrived in Des Moines on Tuesday afternoon.
"Leaving behind your country is not easy, but this was a decision that I gave a lot of thought," Siverio told El Nuevo Herald in Miami. "Of course, my dream is to play in the majors, and from now on I will start taking the first steps to make it happen."
Rep. Ileana Ros-Lehtinen of Florida also welcomed the 24-year-old Siverio to the U.S. in a post on her Twitter account on Wednesday. A message was left by The Associated Press seeking comment from the Cuban-American Republican.
Siverio was not listed when Team USA released an updated roster for Cuba on Wednesday. Team USA CEO Paul Seiler told the AP that, from Cuba's perspective, Siverio is no longer a member of their delegation.
Seiler and Antonio Becali, the head of the Cuban delegation, declined further comment.
The Cubans are in Iowa to play a team of American college stars in the opener of a five-game set spanning three cities. The set starts Thursday night in Des Moines at the home of the Triple-A Iowa Cubs, marking the first extended series between the two countries in American ballparks since 1996.
Siverio is the latest in a long line of Cuban players who defected to the U.S. Now he hopes to follow in the footsteps of a group of major leaguers who are playing prominent roles for contending teams.
Yoenis Cespedes won the Home Run Derby on Monday night during the All-Star festivities at Citi Field in New York. The 27-year-old outfielder is in his second season with Oakland, which leads the AL West by two games over Texas.
Cincinnati Reds closer Aroldis Chapman pitched a scoreless inning in the National League's 3-0 loss to the American League on Tuesday night. Chapman, one of 18 Cubans on major league rosters at the start of the season, has 21 saves and a 2.79 ERA in 42 games.
Of course, there's also Yasiel Puig, who is off to a sensational start with the Los Angeles Dodgers. The 22-year-old centre fielder is batting .391 with eight homers and 19 RBIs in 38 games.
Siverio's defection overshadows what American and Cuban officials are hoping will be a celebration of a decades-old rivalry brought back to life.
The countries played each other in international friendlies from the late 70s until the mid-90s. Cuba also has played World Baseball Classic games in the U.S. and faced the Baltimore Orioles in Camden Yards in a memorable exhibition in 1999.
The matchup between Cuba's national team and American college players resumed last year in Havana, with the Cubans taking three of the five games.
The teams will play a pair of games in Omaha on July 19-20 before one game each in Cary and Durham, N.C.
"It was just a great opportunity to re-ignite what both ourselves and the Cuban federation believed is the two best baseball playing countries going at it," Seiler said at a press conference Wednesday, hours before news broke of Siverio's defection. "We view Cuba as the international benchmark for competition, and we believe they look at us the same way."
Associated Press reporter Barbara Rodriguez contributed to this report.