DUBAI (Reuters) - Abu Dhabi is expected to sell $2 billion in seven-year U.S. dollar-denominated bonds on Tuesday and has tightened the price guidance by 20 basis points after it received over $6 billion in orders, a document showed. Guidance was revised to 50-55 bps over U.S. Treasuries from 70-75 bps over Treasuries earlier in the day, according to the document from one of the banks on the deal, which is expected to launch later in the day. Reporting by Yousef Saba; Editing by Alison Williams Our Standards: The Thomson Reuters Trust Principles.