The following is the Jan. 4, 2024, Congressional Research Service report, Arms Sales: Congressional Review Process.
From the report
This report reviews the process and procedures that apply to congressional consideration of foreign arms sales proposed by the President. This includes consideration of proposals to sell major defense equipment, defense articles and services, or the retransfer to third-party states of such items. Under the Arms Export Control Act (AECA), the President must formally notify Congress 30 calendar days before the Administration can take the final steps to conclude a government-to-government foreign military sale of major defense equipment valued at $14 million or more, defense articles or services valued at $50 million or more, or design and construction services valued at $200 million or more. In the case of such sales to NATO member states, NATO, Japan, Australia, South Korea, Israel, or New Zealand, the President must formally notify Congress 15 calendar days before the Administration can proceed with the transaction. However, the prior notice threshold values are higher for sales to these destinations.
The President must formally notify Congress of commercially licensed arms sales 30 calendar days before Department of State issuance of export licenses for sales of major defense equipment valued at $14 million or more, or defense articles or services valued at $50 million or more. In the case of such sales to NATO member states, NATO, Japan, Australia, South Korea, Israel, or New Zealand, the President must formally notify Congress 15 calendar days before proceeding with the transaction. As with government-to-government sales, the prior notice threshold values are higher for sales to these destinations. The President must formally notify Congress of commercially licensed sales of firearms controlled under category I of the United States Munitions List and valued at $1 million or more 30 days prior to approval of the relevant export license. In the case of proposed licenses for such sales to NATO members, Japan, Australia, South Korea, Israel, or New Zealand, the AECA requires 15 days prior notification.
The AECA contains a mechanism for Congress to adopt a joint resolution of disapproval for arms sales notified by the President; Congress has never successfully blocked a proposed arms sale via such a resolution. Congress may adopt legislation to block or modify an arms sale at any time up to the point of delivery of the items involved.
Download the document here.