United officials said they did not want to comment.
United already employs a Venezuelan midfielder, Júnior Moreno, who is entering his fourth MLS season. Bolívar could compete for first-team minutes but might also spend time with Loudoun.
After remaining quiet much of the winter, United is adding players before training camp opens Monday in Washington.
The club is finalizing a loan for U.S. defender Brendan Hines-Ike, who has played the past five years in Sweden and Belgium. He arrived in Washington over the weekend.
United was also reportedly in the market for Nigel Robertha, a Dutch-born forward for Bulgarian club Levski Sofia.
The team signed a first-round draft pick, Wake Forest defender Michael DeShields, and was close to finalizing a deal with another first-rounder, Clemson attacker Kimarni Smith.
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