According to Axios, the two sides are close to agreeing on a "one-page memorandum of understanding to end the war and set a framework for more detailed nuclear negotiations."

It said the deal would involve Iran committing to a moratorium on nuclear enrichment and the United States agreeing to release billions of dollars of frozen Iranian funds.

Washington is reportedly awaiting a response from Tehran on several key points in the next 48 hours.

"Nothing has been agreed yet, but the sources said this was the closest the parties had been to an agreement since the war began," Axios said.