The Pentagon is set to notify the US Congress of a $60bn (£39bn) weapons sale to Saudi Arabia, reports quoting US officials say.
The deal to sell advanced military aircraft to the Saudi kingdom is aimed at shoring up an Arab ally against Iran, the Wall Street Journal reported.
The arms deal, set to support 75,000 US jobs, would be among the largest yet.
The notification will set off a review where lawmakers could push for changes, impose conditions or block the trade.
Pentagon spokesman Col Dave Lapan said Congressional notification was expected within "the next week or so" but he declined to comment on details of the proposed package.
The BBC's Paul Adams in Washington says the administration is unlikely to encounter much opposition to the sale of weaponry to a traditional ally and will probably argue that it is all part of a strategy to bolster friendly Arab governments in the face of growing strategic threats from Iran.
Off the record, defence officials say the administration will authorise the sale of dozens of aircraft, including F-15 fighter jets and Apache, Black Hawk and Little Bird helicopters.
Saudi Arabia would reportedly initially purchase about $30bn worth of aircraft, but could buy more at a later date.
Balance of power
An unnamed defence official told Reuters news agency that the deal would give Saudi Arabia a "whole host of defensive capabilities to defend the kingdom".
He added that Israel, a firm ally of the US, was "fairly comfortable" with the arrangement.
Meanwhile state department spokesman Philip Crowley said that the US "would do nothing that would upset the current balance (of power) in the region".
The administration is required to notify the Congress in advance of arms sales. Lawmakers have 30 days from notification to object to the deal.
Congressional officials warned that lawmakers could try to block the deal, but analysts say the prospect of job growth in the US defence industry could be another encouragement for lawmakers to approve it.
The UK sold major combat aircraft to the Saudis in 1980s, when the US chose not to.
Saudi Arabia is one of the top buyers of weapons in the developing world, purchasing an estimated $36.7bn in arms between 2001 and 2008, according to the Congressional Research Service.