The Unites States will keep working on a regional missile defense system in Persian Gulf despite progress on the Iran nuclear deal, current and former U.S. military officials said on Thursday while warning that Iran has the largest inventory of short- and medium-range cruise and ballistic missiles in the region.

The comments came as a Republican-backed effort to kill the Iran nuclear agreement was narrowly blocked in the U.S. Senate, handing President Barack Obama a huge victory and clearing the way for the deal's implementation.

Robert Scher, assistant defense secretary for strategy, plans and capabilities, told lawmakers the Pentagon would continue to push for cooperative missile defense programs since the nuclear deal did not cover Iran's work on ballistic missiles.

"There is no doubt in my mind that Iran's ballistic missile activities continue to pose a risk to the United States and our allies and partners in Europe, Israel, and the Gulf," he told the House Armed Services Committee's strategic forces subcommittee.

U.S. Air Force Brigadier General Kenneth Todorov, who stepped down six weeks ago as deputy director of the U.S. Missile Defense Agency, said he saw growing momentum for a Gulf missile shield.

"The worst mistake we could make if the deal happens is to say, 'We can let our guard down,'" he told an event hosted by the Missile Defense Advocacy Alliance, a non-profit group that lobbies for missile defense programs.

President Obama and allies from the six-nation Gulf Cooperation Council (GCC) underscored their commitment to build the defense system at a May summit, as Washington moved to assuage Gulf allies' concerns about a more powerful Iran once international trade and financial sanctions are lifted.

Todorov said building a truly integrated system required greater cooperation among GCC countries, and hard work on integrating existing systems already present in the region.

One relatively "doable" target would be to integrate missile early warning systems already in use by individual countries.

Michael Tronolone, former director of the U.S. Central Command Integrated Air and Missile Defense Center of Excellence in Abu Dhabi, said it was imperative for U.S. officials and Gulf allies to share data about potential threats, arguing that advances in cyber security had reduced the risks involved.

The biggest obstacles, he said, were not technologies but policy barriers that prevented more multilateral efforts.

"To hook those sensors together will increase our capabilities exponentially," said Tronolone, who now works for U.S. weapons maker Raytheon Co (RTN.N).

He said a Gulf missile shield would also require construction of a warehouse with spare parts in the region, since it now takes one to two years to repair damaged missiles because they are all sent to the United States.

Tronolone also called for more multilateral training.

He said the focus was less on buying new weapons systems than taking steps to break down barriers and better coordinate among GCC countries.

Last week's attack in Yemen that killed 50 soldiers from the United Arab Emirates and Bahrain would help cement ties among Gulf states that have not always seen eye to eye, he said.

By Reuters