U.S. President Donald Trump has authorized a “moderate” bolstering of U.S. forces in Saudi Arabia and the United Arab Emirates (U.A.E.) following the attack on Saudi oil infrastructure that many in the administration have blamed on Iran.

The Pentagon on September 20 said it has not decided on the specific units to be sent to the region and it did not specifically mention any potential military action against Iran.

Defense Secretary Mark Esper said the action was a response to requests from the Saudis and the U.A.E. to help improve their air and missile defenses. He said the troops' mission would be "defensive in nature."

"To prevent a further escalation, Saudi Arabia requested international support to help protect the kingdom’s critical infrastructure. The United Arab Emirates has also requested assistance." Esper said.

He stressed it was a first step and that he was not ruling out additional moves in the future, and General Joseph Dunford, chairman of the Joint Chiefs of Staff, said details of the deployments will be determined in the next few days.

Esper added that Washington "does not seek conflict with Iran" but that it would be prepared for any situation.

In July, the United States said it was sending some 500 troops to Saudi Arabia as part of a broader move to increase its force in the Middle East following a spate of attacks on oil tankers in the Gulf of Oman that Washington blamed on Iran or its proxies.

Tensions in the region soared again following the September 14 drone and missile attack on the world's biggest crude oil-processing plant in Saudi Arabia, a strong U.S. ally and fierce regional rival of Iran.

Riyadh and several U.S. administration officials, including Secretary of State Mike Pompeo, have asserted that Tehran was behind the attack.

Iran-backed Shi'ite Huthi rebels in Yemen said they were behind the September 14 attack.

But Washington and Riyadh have blamed Tehran directly. Sunni-majority Saudi Arabia, which is leading a coalition of Arab states fighting against the Huthis, on September 18 put on display drone and missile fragments that it said were used in the attack and said they implicated Tehran.

Iran has denied involvement and warned the United States that any attack would lead to an "all-out war" with Tehran.

U.S. media had reported that the Pentagon was set to present a wide range of military options to Trump on September 20 as the president considers how to respond to the attack on Saudi Arabia’s oil industry.

The reports said the military would present Trump with a list of potential air-strike targets inside Iran, among other possible responses.

Officials inside and outside the U.S. administration had said the response could involve military, political, and economic actions, and that military options range from no action to air strikes or moves such as cyberattacks.

Washington could also provide additional military support to help Saudi Arabia defend itself from attacks from the north. Most of Riyadh’s defense efforts have focused on threats from Huthi rebels in Yemen in the south of the peninsula.

Earlier on September 20, Washington announced it had imposed another round of sanctions on Iran, including on its central bank and its sovereign wealth fund, following the Saudi attack.

Describing the measures as the highest sanctions ever imposed on a country," Trump signaled he was not inclined to authorize an immediate military action on Iran in response to the drone and missile attack.

With reporting by AP, AFP, Reuters, and dpa