The Trump administration informed congressional committees on Friday that 22 military sales worth $8 billion will go ahead to the Saudis, United Arab Emirates and Jordan.
The move that has infuriated lawmakers, Trump circumvented a long-standing precedent for congressional review of such sales.
In documents sent to Congress, Secretary of State Mike Pompeo listed a wide range of products and services that would be provided to the three countries.
They include Raytheon precision-guided munitions (PGMs), support for Boeing Co F-15 aircraft, and Javelin anti-tank missiles, which are made by Raytheon and Lockheed Martin Corp.
Some lawmakers and congressional aides had warned earlier this week that Trump, frustrated with Congress holding up weapons deals like the sale of the Raytheon-made bombs to the Saudis, was considering using a loophole in arms control law to go ahead by declaring a national emergency.
Lawmakers had been blocking sales of offensive military equipment to Saudi Arabia and the United Arab Emirates for months.
This was due to concerns about the huge civilian toll of the two countries' air campaign in Yemen and human rights abuses like the murder of Saudi journalist Jamal Khashoggi at a Saudi consulate in Turkey.
Congressional sources said Friday's order included all the defence equipment that members of Congress had been blocking.
"I am disappointed, but not surprised, that the Trump Administration has failed once again to prioritise our long-term national security interests or stand up for human rights, and instead is granting favours to authoritarian countries like Saudi Arabia," Senator Bob Menendez said in a statement, who reviews such sales.
Another, the Republican Foreign Relations Committee chairman, Senator Jim Risch, said he had received formal notification of the administration's intent to move forward with "a number of arms sales."
In a statement, Risch said: "I am reviewing and analysing the legal justification for this action and the associated implications."
The White House and State Department did not immediately respond to requests for comment.
In his memorandum to Congress justifying the sale, Pompeo listed years of actions by Iran.
"Iranian malign activity poses a fundamental threat to the stability of the Middle East and to American security at home and abroad," he wrote, and cited "a number of troubling and escalatory indications and warnings" from Tehran.
Congressional aides questioned the contention that the weapons had to do with Iran, saying the equipment and services listed by the administration includes large amounts of offensive weapons, like the PGMs and tank ammunition.
They said lawmakers have not been blocking defensive equipment such as Patriot missile defence systems that have been sold to the Saudis.
"This is all materiel that arguably could be used in the Yemen military operation. The defensive stuff we've cleared," one congressional aide said.