FILE - In this Monday, Aug. 11, 2014 file photo, F/A-18 fighter jets take off for mission in Iraq from the flight deck of the U.S. Navy aircraft carrier USS George H.W. Bush, in the Arabian Gulf. Image Credit: AP

Riyadh, Saudi Arabia: The United States is negotiating cost-sharing terms with Saudi Arabia for an expanding military mission aimed at ensuring the kingdom is protected from attacks on critical oil infrastructure, officials said.

The Pentagon’s deployment of new radar, air defense and other military assets to the Gulf nation was discussed during talks Gen. Mark Milley, chairman of the Joint Chiefs of Staff, held with Saudi officials this week.

Milley, in his first visit to this key US ally since becoming President Donald Trump’s chief military adviser this fall, met with Crown Prince Mohammed bin Salman and other leaders during his visit.

Trump authorized a boost to the relatively light US footprint in Saudi Arabia, from an advisory mission that stood around 800 to a force of about 3,000, following the Sept. 14 assault on Saudi oil facilities, which Saudi and US officials said was launched by Iran in an major escalation of regional tensions.

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The troops will operate additional assets designed to help the Saudi military guard against Iranian attacks, including four Patriot batteries, a THAAD air defense system and two squadrons of fighter jets.

The officials, who spoke on the condition of anonymity, said the two countries are negotiating “burden-sharing” arrangements but the kingdom is expected to provide financial support for some elements of the expanded US military presence, including upgrades to a major air base, fuel, water and logistics.

Military officials say the deployment has a dual purpose: to fill in gaps in the Saudi Arabia’s air defense network, which in recent years has been oriented southward toward threats from Houthi rebels in Yemen rather than east or north toward Iran, and to prevent any potential Iranian action by raising the stakes.

Speaking to reporters traveling with him on a tour of Middle Eastern nations, Milley said it was important for potential adversaries to have a clear understanding that the United States was willing to employ force if required.

“So we want to maintain significant military capability within the region to reassure allies and deter Iran from aggression,” he said.

“As long as Iran knows we’ll use it, I think it’ll be effective.”

Deployment reflects worry

The US troop presence in Saudi Arabia remains a modest part of an overall regional footprint that exceeds 60,000, but officials say the new deployments reflect a worrying uptick in Iranian attacks.

The incidents also include mine attacks on Arab and European vessels.

In June, Trump authorized but then called off a strike on Iranian targets after Iran shot down an American drone that it said had veered into its airspace.

Iran denied involvement in the September attack, for which Yemeni Houthi rebels linked to Tehran initially asserted responsibility.

Military officials say one important aspect of the deployment is the presence of American forces in more locations across the kingdom.

Iranian reluctance

They believe Iran has demonstrated its reluctance to target American personnel, either directly or indirectly, in part because Trump has made clear that would trigger a military response.

“When you internationalize . . . it makes it harder for the Iranians to lash out because they’re now not just lashing out at a [Gulf] country,” a senior defense official said.

The Iranian reluctance is a change from the years following the 2003 US invasion of Iraq, when US officials estimate Iranian backed militias killed at least 500 American troops.

Now, American forces say, Iran seeks to strike back against sanctions imposed by the Trump administration, which have taken a severe toll on its economy and jeopardized its ability to finance armed proxies in the region.