WASHINGTON — Nine Democrats in Congress are threatening to block a proposed American arms sale to Saudi Arabia that would equip the kingdom with satellite-guided missiles more accurate than any technology now in the Saudi air force.

The proposed sale of Joint Direct Attack Ammunitions to Riyadh was first announced in April by Defense Secretary Gates on a trip to Jerusalem, where he assured Israeli leaders that the Jewish state would maintain its qualitative air power advantage over the Arab states.

Nonetheless, Rep. Anthony Weiner, a Democrat of New York, and his Democratic colleague from Florida, Robert Wexler, are expressing concern at the sale.

Yesterday they threatened to invoke the 1976 Arms Export Control Act to block the sale “the minute the deal is announced.”

A press release from Mr. Weiner’s office claimed that 500 Saudi youths have traveled to Iraq to wage a “holy war,” and it blamed Saudi diplomats for having “torpedoed” a proposed Arab-Israeli peace summit in April.

“We need to send a crystal clear message to the Saudi Arabian government that their tacit approval of terrorism can’t go unpunished,” Mr. Weiner said. “Saudi Arabia should not get an ounce of military support from the U.S until they unequivocally denounce terrorism and take tangible steps to prevent it.”