It follows settlements by European rivals Credit Suisse and Lloyds as US authorities probe banks' dealings with restricted countries such as Iran.
The DoJ, the New York County District Attorney's Office and the Office of Foreign Assets Control have been investigating Barclays, and the UK bank said in its first-half results on Thursday it was in advanced discussions to resolve the probe.
The bank set aide the provision "in the possible resolution of this matter." It refused to comment further.
In December Credit Suisse said it would pay $539 million to settle charges it failed to comply with US laws and Lloyds reached a $217 million settlement of charges it violated US sanctions regulations.
Court documents accused Credit Suisse of violating US laws by moving hundreds of millions of dollars illegally through the US financial system on behalf of sanctioned countries such as Iran. The Lloyds settlement followed charges it faked records so clients from restricted countries could do business with it.
