If Egypt's Anwar Sadat is, as Jimmy Carter says, the "world's foremost peacemaker," why is the administration in such a hurry to send him an armada of war planes?

It's a tantalizing question, but only a sample of many others that are going to be thoroughly chewed over when a skeptical Congress begins debating Carter's $4.8-billion Mideast arms package, which includes planes for Israel and Saudi Arabia as well as Egypt.

Rough as the argument may be, it could have constructive results if it finally helps Congress to clarify its often muddled thinking on the difficult problem of arms sales, not only in the Middle East but all over the globe.

The situation stems from the welcome trend on Capitol Hill to put legislative restraints on the arms traffic and the disposition of military and economic aid. If, however, Congress is going to impose its views in these critical areas, it ought to make up its mind what it wants, even though the White House itself has pursued an uncertain, inconsistent policy on arms transfers.

Both the president and Congress are plagued by goals that are frequently incompatible. Should the sale or withholding of arms be linked to our moralistic policy of advancing human rights in other countries? Or should realpolitik prevail, with sales subordinated to presumed U.S. national security interests regardless of the character of the buying nation?

Both the Senate and House are currently wrestling with this dilemma trying to decide whether to approve the administration's $2-billion aid package - including $800 million in weapons - for South Korea.

The military government in Seoul is antidemocratic and harshly repressive of human rights. In fact, the U.S. State Department in a report to Congress has just cited South Korea for continuing violations of human rights. Moreover, the Hill is aroused over the Korean government's efforts to obtain more aid funds by bribing members of Congress.

Only a few days ago, Rep. Clement Zablocki (D-Wis.), chairman of the International Relations Committee, said the House would not even consider Carter's weapons pacakge for South Korea because of that government's refusal to cooperate with the congressional bribery investigation. The Senate majority leader, Sen. Robert Byrd, also said Seoul is risking the loss of aid.

Nevertheless, the administration, despite its proclaimed dedication to human rights, feels South Korea's armed forces should be strengthened to compensate for the gradual withdrawal of U.S. armed forces from the Korean peninsula.

The Senate Foreign Relations Committee seems to agree. Splitting with Zablocki and Byrd, the committee has just released a report urging Congress to avoid linking military needs of the region to the bribery expose.

"Long-term U.S. political alignments in the whole East Asian region," the report says, "must not be jeopardized for the short-term objectives of the scandal investigation."

Korea's human-rights problems, it adds, "should be put into perspective." Jimmy Carter couldn't have put it more blandly. A lot of "perspective" hs gone into his Mideast arms program, which includes 60 F-15 planes (worth $2.5 billion) for Saudi Arabia, which is hardly a civil- or human-rights paradise.

On Saudi Arabia, unlike Korea, the president faces opposition from the Senate Foreign Relations Committee - or did a couple of weeks ago when the committee by a 10-to15 vote urged the administration to drop the proposed sale of F-15s to the Saudis on the grounds that it would destablize the balance of power in the region.

The president himself has spent the last year wavering on the deal, as he has on his whole arms program. He came to office pledged tocurb arms sales, but in the last fiscal year (ending Sept. 30) they rose to $11.2 billion, and are now headed for $13.2 billion or more in the current fiscal year.

When establishing U.S. policy on arms transfers, Carter last May said "the virtually unrestrained spread of conventional weaponry threatens stability in every region of the world." He deplored this as a "threat to world peace."

At the same time, however, he also said the United States "would continue to utilize arms transfers to promote our security and the security of our close friends." Herbert Schandler, a retired Army colonel who was one of the authors of a recent Library of Congress study on Carter's arms-sales fluctuations, summed it up this way:

"The president has found it less difficult to announce a bold policy initiative of high moral purpose in the arms-transfer field than to put those policies into practice."