WASHINGTON (AP) — 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 US 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 US protection.

The administration will send a review of ballistic missile strategy to Congress on Monday that frames the larger shifts. Attention to defense of the Persian Gulf region, a focus on diffuse networks of sensors and weapons and cooperation with Russia are major elements of the study, according to documents obtained by The Associated Press.

Russia opposed Bush administration plans for a land-based missile defense site in Eastern Europe, and President Barack Obama's decision to walk away from that plan last year was partly in pursuit of new capabilities that might hold greater promise and partly in deference to Russia.

One military official said the adjustments in the Gulf should be seen as prudent defensive measures designed to deter Iran from taking aggressive action in the region.

Secretary of State Hillary Rodham Clinton consulted with numerous allies during a visit to London last week. She told reporters that the evident failure of US offers to engage Iran in negotiations over its nuclear program means the US will now press for additional sanctions against the Iranian government.

Gen. David Petraeus, the US Central Command chief who is responsible for US military operations across the Middle East, mentioned in several recent public speeches one element of the defensive strategy in the Gulf: upgrading Patriot missile systems, which originally were deployed in the region to shoot down aircraft but now can hit missiles in flight.

In remarks at Georgetown Law School on Jan. 21, Petraeus said the US now has eight Patriot missile batteries stationed in the Gulf region — two each in four countries. He did not name the countries, but Kuwait has long been known to have Patriots on its territory.

A military official said Saturday that the three other countries are the United Arab Emirates, Bahrain — which also hosts the US Navy's 5th Fleet headquarters — and Qatar, home to a modernized US air operations center that has played a key role in the Iraq and Afghanistan wars.

In a presentation Jan. 22 at the Institute for the Study of War, Petraeus explicitly linked the actions to concerns about Iran.