Raytheon Co , one of the largest U.S. weapons makers, is expected to sign an estimated $2.1 billion deal to sell Oman an air defense system while U.S. Secretary of State John Kerry visits the Gulf state this week, U.S. officials said.

One official, who spoke on condition of anonymity, told reporters the company was expected to sign a letter of intent with Oman to provide a ground-based air defense system.

The official said the terms were still being negotiated and the deal's value was not yet final.

(Reporting by Arshad Mohammed; Editing by Eric Beech)