Yes. The U.S. AG can decline to prosecute an indictment at any time until jeopardy attaches when a jury is sworn in to consider the charges at trial. The AG can also abandon a prosecution mid-trial but then cannot retry those charges later.
The AG might abandon charges, for example, because the evidence does not appear to support the charges when presented at trial, or because, for example, a prosecution might damage a diplomatic relationship of the U.S. with another country, or because a new administration has different priorities than an old one and recently had its AG appointed to office while the trial was pending.
This said, there are some situations (e.g. when there is a special prosecutor, or after a lower level prosecutor has entered into a binding plea agreement) when the AG does not have the authority to overrule the decisions to prosecute or not prosecute an indictment that is made by a lower level prosecutor. The AG has line authority to give orders to lower level prosecutors in the AG's office 99% of the time, but not always.