Vice President Bush, citing Anwar Sadat's death as "the loss of a great friend," said yesterday that the United States faces a "historical decision" about whether it will "honor a commitment to another friend in the Middle East, Saudi Arabia," by selling sophisticated radar planes to the Saudis.

In a luncheon speech at the National Press Club, Bush pushed the argument advanced by the administration in the wake of Sadat's assassination. Its main point is that Sadat's death makes doubly urgent the need for Congress to approve President Reagan's proposed sale of Airborne Warning and Control System (AWACS) planes to help cultivate Saudi friendship.

Thad Cochran (R-Miss.) yesterday became the 10th senator since Sadat's murder Tuesday to declare his support of the $8.5 billion sale. But he, like eight of the others, had been considered likely to support the administration, and congressional head-counters said Reagan still is far short of the majority needed to block a Senate veto of the deal.

The Saudi aircraft package, the largest arms sale in history, will be blocked if both houses of Congress vote against it before the end of the month. The administration concedes it has no chance of prevailing in the Democratic-controlled House and has staked its hopes on reversing a hostile majority in the Republican-dominated Senate.

That goal led Bush to conclude his speech with an appeal to the American public: "I ask that you act now and let your representatives in the House and the Senate know how you feel . . . . I hope, in these critical times, that you will support your president, your country and the cause of peace among the peoples of the world."

In his main text, Bush recapped the administration's now-familiar arguments that the sale is necessary for U.S. strategic plans to protect Saudi oil fields, that the credibility of Reagan's leadership in world affairs requires honoring the commitment and that AWACS planes and other aircraft equipment in the sale pose no danger to Israel.

Regarding Israel, Bush said, "If these planes were a significant threat to Israel, we wouldn't be selling them to Saudi Arabia. It's that simple. Those who say otherwise are ignoring the fact that President Reagan is one of the best American friends Israel has ever had."

Then, in words reminiscent of Reagan's warning last week that Israel should avoid interfering in U.S. affairs, Bush said: "We will stand by Israel. But at the same time we cannot--we will not--ignore our friends and vital interests elsewhere in the Middle East."

Bush also harshly attacked Libyan leader Muammar Qaddafi, calling him "an egomaniac who would trigger World War III to make headlines."

The administration repeatedly has singled out Qaddafi as an instigator of subversion and turmoil in other countries and has called him a "surrogate" of the Soviet Union.

Rhetorical U.S. attacks on Qaddafi have been escalating since Libya, in the wake of Sadat's assassination, called on the Egyptian people to revolt against his successors.

"He's the world's principal terrorist and trainer of terrorists," Bush said of Qaddafi. "He's the protector of the likes of Idi Amin the deposed Ugandan dictator accused of wholesale murder . He's dangerous--to Egypt, to Israel, to peace."