The United States government sent a letter to Sweden warning of “negative consequences” in the relationship between the countries if Sweden did not release the rap artist ASAP Rocky from prison.

The rapper, whose real name is Rakim Mayers, went on trial for assault this week along with two other men, David Rispers and Bladimir Corniel . They were released on Friday at the conclusion of the trial while a verdict is pending.

The letter, which was dated July 31, was signed by Robert O’Brien, special envoy for hostage affairs.

Mr. O’Brien wrote to Swedish officials that “the government of the United States of America wants to resolve this case as soon as possible to avoid potentially negative consequences to the U.S.-Swedish bilateral relationship,” according to NBC News, which obtained a copy of the letter.