Solo told the Associated Press in an interview released Thursday the governing body of the sport in America has "too many conflicts of interest that need to be addressed immediately."
"I can't say it should be awarded to Morocco," she said. "But I don't think it should go to the United States, and that's hard to say."
Morocco and a joint bid between the United States, Canada and Mexico are the only official proposals to host the 2026 World Cup ahead of next Wednesday's vote. Member nations can also choose "none of the above" if they feel the process should be reopened, according to the AP.
"Hopefully FIFA can stand up and step in and say, 'If we're going to reward you, let's look at everything and point out where you can fix certain things,'" Solo said.
The two-time Olympic gold medalist and 2015 World Cup champion added she recently visited Washington, D.C., for discussions with lawmakers about making sure U.S. Soccer is "run transparently, has integrity and is an open and honest national governing body."
In August 2016, Solo called the Swedish women's team a "bunch of cowards" after it beat the USWNT on penalties in the quarterfinals of the 2016 Summer Olympics. She received a six-month suspension and had her contract with the national team terminated soon after.
While the 36-year-old Washington state native hasn't returned to the national team, she ran for president of U.S. Soccer in February's election. She came up well short, however, with just 1.4 percent of the vote on the final ballot—Carlos Cordeiro was chosen for the role.
Solo earned 202 caps for the United States before her dismissal.
The U.S. is attempting to secure its second World Cup. It previously hosted the event in 1994.