Congress left town last month expecting to vote on arms limitation when it returned. Instead, it will reconvene next week preoccupied with arms expansion.

At President Carter's request, the Senate has shelved the Strategic Arms Limitation Treaty for the foreseeable future, in response to the Soviet invasion of Afghanistan.

The first order of business in both House and Senate in what has already been called this "post-Afghan Congress" will be a slap at the Soviet Union -- action on the administration's proposal to normalize trade relations with the People's Republic of China, according it a nondiscriminatory status never given the Soviets.

Proposals made last fall to extend this most-favored-nation status to the Soviets as well in a spirit of even-handedness will not be heard. Congress instead will vote on military aid to the Pakistanis, who were denied it last year for fear they are developing anuclear bomb, and arms to the Saudis and perhaps the Turks as well.

Increases in this country's defense budget will also come early on the agenda.

"I think there has been a big change"in the congressional atmosphere, said Senate Majority Leader Robert C. Byrd (D-W.Va.) in an interview last week. "I wouldn't call it a war-minded Congress" as some of his colleagues did, "but it certainly will be a Congress that is security-minded and more so than before Afghanistan."

Sen. George McGovern (D-S.D.), a leading dove, agreed: "Whatever the administration proposes or whatever has administration backing -- the B1, neutron bomb, MX missile or whatever -- it will go through this Congress with a whoop and a holler." He thinks there will be a big push in Congress to build up the military, reflecting a "regretful return to the Cold War mentality."

Interviews with other available members suggest a strong possibility that congressional preoccupation with national security this year could further squeeze social programs that hadtough enough going last year. But it is too early to say with certainty. A year ago Congress was all fired up about forcing a balanced budget. But nothing happened.

Congress was already expecting a $20 billion increase in the administration's defense budget request and that seems likely to be raised during the year to counter the perceivedSoviet threat in the Mideast oil region.

Rep. Joseph P. Addabbo (D-N.Y.), chairman of the House Appropriations defense subcommittee whowas an early opponent of the Vietnam war and an eager hunter of fat in the defense budget, was skeptical of the need for vast new military-industrial complex can always come up with 42 ways to spend more money even though they couldn't use it if they had it," he said. But he expects the pressure to be great.

The Soviet aggression also seems to assure congressional approval of aid to Pakistan on Afghanistan's southern border, arms sales to Saudi Arabia and additional aid if needed to Turkey.

And "if we have to shore-up nations like Pakistan, Saudi Arabia and Turkey, we can't make human rights the cornerstone of foreign policy," noted a House staff member. "Defense becomes the main consideration of foreign policy. Afghanistan guarantees a national security consensus and higher defense spending."

Congress had cut off aid to Pakistanbecause it was developing nuclear weapons. The House Foreign Affairs Committee has scheduled a hearing Tuesday on the administration's $400 million aid package and plans voting on the first $200 million of it within afew days.

Just before the end of last session the administration sent Congress, for possible veto, a plan to sell arms to Saudi Arabia, the biggest oil producer in the Mideast.

There was some talk then of disapproving it on grounds that if the Saudi government were overthrown this would bethrowing more money down a rathole as was the case of arms sold to the deposed shah of Iran. Now the emphasis should shift to the need to help these nations defend themselves.

For more than five years there has been a fierce fight in Congress over aid to Turkey because of that country's invasion of Cyprus with American arms and its dispute with Greece. The embargo on aid to Turkey has been lifted and any request for more aid to this country on the Soviet border would probably have easy going now.

The aggressive move by the Soviets can be expected to help efforts to give the CIA more flexibility in carrying out covert activities. They must now be reported to eight congressional committees. The administration would like to reduce the potential for leaks.

Support for reviving the military draft, or at least registering all draft- age persons so it could be quickly activated if needed, probably will increase in this new climate. But Congress is not likely to vote a military draft in election year. Sen. Mark Hatfield (R.-Ore.) said he would filibuster it. Proposals will be made to raise military pay and cut it loose from civilian government workers' pay levels.

Soviet moves south near Mideast oil fields are also expected to speed final action on major energy bills by portraying energy more vividly than before as a national security issue. Still locked in House-Senate conference committees are bills to encourage production of alternative energy sources, speed action on new energy projects and tax domestic crude oil.

House and Senate committees will start hearings immediately to take a look at the new picture. The House Foreign Affairs Committee plans hearings next week on Afghanistan and the president's embargo on further grain sales to the Soviet Union in addition to the Pakistan aid package.

The Senate Foreign Relations Committee will be briefed by Secretary of State Cyrus R, Vance Monday and plans comprehensive hearings soon on Iran, where a revolutionary regime has held 50 American hostage in the U.S. Embassy since Nov. 4.

The Senate Armed Services Committee plans hearings this week on Soviet defense spending and the Senate Energy Committee on the adequacy of oil supplies.

All this seems likely to cost a lot more money at a time when there is heavy sentiment to hold down government spending to fight inflation. If defense spending goes up, spending for social programs must go down or the inflationary deficit grows.

It is the old choice of guns or butter. When Lyndon Johnson decided during the Vietnam war to have both, the budget deficit got out of hand.

But President Carter just recently called for a $2 billion increase in money to provide youth jobs. Byrd said it should be possible to have both guns and butter "to a certain extent" because the oil tax will bring in a lot of money.

But Rep. James Jones (D-Okla.), who has led the fight to impose spending limits, said the expected increased national security spending provides a stronger argument than before for making choices and not give in to inflationary increased government spending.

There is also a lot of domestic legislation waiting congressional action. Bills are in final stages, such as standardizing and expanding refugee programs, and may be enacted quickly. Others, such as welfare reform and national health insurance would cost a lot of money and may not make it. The Senate Finance Committee plans to try again to put together a bob-tailed health bill to cover costs ofcatastrophic illness.

Also in conference are bills passed by both bodies to increase price supports on some farm crops and to deregulate the banking industry.

A program of aid to chronically depressed cities is ready for a House vote, as is a bill to help build slurry pipelines to move pulverized coal long distances. The railroads and environmentalists combined for opposite reasons to kill the pipeline bill in the last Congress.

Congress is also expected to take a close look at the Social Security tax structure. Under a law passed two years ago to shore up the Social Security trust fund, both the tax rate and tax base for the levy that finances Social Security benefits will jump next January, costing workers at the top level nearly $400 a year in additional payments.

There have been proposals to roll back the increase in the rate or to finance part of Social Security, such as health benefits, from general revenues.