The Washington Post reports that Congress was officially notified of the proposed sale on 5 May, citing three people familiar with the notification — a week before the current conflict with Hamas began.
Rockets fired from Gaza into Israel have led to the deaths of 10 Israelis. Airstrikes on Gaza have left almost 200 Palestinians dead.
The Biden administration has called for a ceasefire but also maintains that Israel has the right to defend itself.
While a large majority of Congress backs this position, a growing minority of Democrats, particularly in the House of Representatives, have raised concerns about supporting Mr Netanyahu and question the timing of the sale.
Some suggest using the sale as leverage to push for a ceasefire.
“In the past week, the Israeli military's strikes have killed many civilians and destroyed the building that housed the Associated Press, an American company reporting on the facts in Gaza,” a Democratic lawmaker on the House Foreign Affairs Committee told the Post.
“Allowing this proposed sale of smart bombs to go through without putting pressure on Israel to agree to a cease-fire will only enable further carnage.”