Washington ? As the Obama administration edges toward imposing tougher sanctions on Iran, it has begun upgrading its approach to defending its Persian Gulf allies against potential Iranian missile strikes, officials said Saturday.

The United States has quietly increased the capability of land-based Patriot defensive missiles in several Gulf Arab nations, and one military official said the Navy is beefing up the presence of ships capable of knocking down hostile missiles in flight.

The officials discussed aspects of the defensive strategy on condition of anonymity because some elements are classified.

The moves have been in the works for months and are part of a broader adjustment in the U.S. approach to missile defense, including in Europe and Asia. Details have not been publicly announced, in part because of diplomatic sensitivities in Gulf countries which worry about Iranian military capabilities but are cautious about acknowledging U.S. protection.

The administration will send a review of ballistic missile strategy to Congress on Monday that frames the larger shifts.