The Trump administration has invoked an emergency provision of the law governing arms sales to immediately sell Saudi Arabia and other Gulf allies weapons without congressional approval, senators said Friday.

The approval comes amid heightened tensions with Iran over what the administration has described as increased threats to U.S. interests in the region, and the senators indicated that Iran was used as justification for the emergency sale.

The administration on Friday also announced the deployment of 1,500 U.S. troops to the Middle East to protect U.S. forces already there from Iran.

The package Congress was notified of Friday is composed of more than 20 separate deals and is valued at $8.1 billion, a Senate staffer told The Hill. The weapons include precision guided munitions, others bombs and ammunition, and aircraft maintenance support, the staffer said.

The arms are being sold to Saudi Arabia and the United Arab Emirates, with the UAE then transferring some to Jordan, the staffer said.

Late Friday afternoon, Secretary of State Mike Pompeo released a statement saying the 22 arms sales are needed to "help these nations to deter and defend themselves from the Islamic Republic of Iran."

"Delaying this shipment could cause degraded systems and a lack of necessary parts and maintenance that could create severe airworthiness and interoperability concerns for our key partners, during a time of increasing regional volatility," he said. "These national security concerns have been exacerbated by many months of congressional delay in addressing these critical requirements, and have called into doubt our reliability as a provider of defense capabilities, opening opportunities for U.S. adversaries to exploit."

Pompeo added that using the emergency provision is intended as a "one-time event."

"Section 36 is a long-recognized authority and has been utilized by at least four previous administrations since 1979, including Presidents Reagan and Carter," he said. "This specific measure does not alter our long-standing arms transfer review process with Congress. I look forward to continuing to work with Congress to develop prudent measures to advance and protect U.S. national security interests in the region."

Notices posted on the Defense Security Cooperation Agency website show the approvals include sales to the Saudis for surveillance aircraft support and maintenance of Saudi aircraft, and to the Emiratis for 20,004 precision guided munitions kits, 331 Javelin anti-tank missiles and 20 RQ-21A Blackjack drones.

The State Department informed relevant Senate and House committees and offices of the decision in a call and also sent to the Senate Foreign Relations Committee Pompeo's determination that an emergency exists requiring the sale in U.S. national security interests, the Senate staffer said.

Senate Foreign Relations Committee Chairman Jim Risch (R-Idaho) said he received the notification and is reviewing the legal justification.

"I have received formal notification of the administration's intent to move forward with a number of arms sales," he said in a statement. "I am reviewing and analyzing the legal justification for this action and the associated implications."

Democrats had warned earlier this week the administration was on the verge of using what they described as an "obscure loophole" in the Arms Export Control Act to finalize a long-stalled arms deal with Saudi Arabia.

Friday's formal notification drew immediate condemnation from top Democrats.

In a four-paragraph statement, Foreign Relations Committee ranking member Sen. Bob Menendez (D-N.J.) slammed the administration as failing "to even identify which legal mechanism it thinks it is using," adding the notification "described years of malign Iranian behavior but failed to identify what actually constitutes an emergency today."

"As I repeatedly warned the Trump administration in the lead up to this ill-informed decision, I will fight any effort to further erode congressional review and oversight of arm sales," Menendez said.

"I am in discussion with several Democratic and Republican colleagues, and I hope the Senate Foreign Relations and the House Foreign Affairs Committees will soon be able to expeditiously address this latest attack on our constitutional responsibilities," he added. "The lives of millions of people depend on it."

In a separate statement, Sen. Chris Murphy (Conn.), the top Democrat on the Senate Foreign Relations subpanel with oversight of the Middle East, said the administration is setting an "incredibly dangerous precedent."

"We have the constitutional duty to declare war and the responsibility to oversee arm sales that contravene our national security interests," Murphy said. "If we don't stand up to this abuse of authority, we will permanently box ourselves out of deciding who we should sell weapons to. I'm currently working on legislation to restrict arm sales so we can get back in this business of helping set critical foreign policy."

The Arms Export Control Act gives lawmakers 30 days to vote to block an arms sale once Congress is formally notified about it.

But the law also says the president can waive the review period and have the sale go through immediately if "an emergency exists which requires the proposed sale in the national security interest of the United States."

Menendez has had a hold on arms sales to Saudi Arabia and the United Arab Emirates since April 2018 over concerns about civilian causalities in the Yemeni civil war. A Saudi-led military coalition that the United States supports with arms sales has been blamed for the majority of civilian deaths in the war.

The hold is an informal process the administration could break. But lawmakers have also warned the administration does not have the votes to get an arms sale through Congress because of anger over the Saudis' killing of U.S.-based journalist Jamal Khashoggi.

Trump has resisted pressure to punish the Saudis over Khashoggi's death, in part arguing U.S. companies will lose out on business from arms sales. Trump has touted an agreement with the Saudis for $110 billion in arms sales as a signature achievement.

This story was updated at 5:53 p.m.