The United States is holding "detailed discussions" with the European Union and United Kingdom to iron out specifics of a price cap on Russian oil, National Security Adviser Jake Sullivan said on Wednesday.

"That is not a process that will be completed in days. It will take time because of the number of elements that have to be worked through," Sullivan told reporters aboard Air Force 1 as President Joe Biden made his way to the Middle East. (Reporting by Ari Rabinovitch)