The MX land missile will require an antiballistic missile (ABM) system to protect it no matter which MX deployment scheme is chosen by President Reagan, the chairman of the Senate Armed Services Committee said last night.

Sen. John G. Tower (R-Tex.) declared, "I think ballistic missile defense is going to be essential regardless of the basing system" for the MX.

Tower added that it would not bother him if the United States had to scrap or mend the existing antiballistic missile treaty with the Soviet Union that limits ABM deployment to 100 intercepting missiles and 18 fixed radars at one site in each country.

By linking the MX and ABM, Tower added fresh fuel to the debate about whether deploying the MX would help deter a nuclear war, as Reagan asserts, or merely heat up the superpower arms race.

Whether to build an ABM defense system was one of the hottest defense issues of the 1960s, with the Senate ultimately forcing the Pentagon to abandon plans for such a defense.

Tower said members of his committee generally accept that "there would be a ballistic missile defense overlay" in any MX deployment scheme.

He had just finished chairing a House-Senate conference that hammered out a compromise defense authorization bill for fiscal 1983. It provides $377 million for missile defense, $350 million less than Reagan had requested.

Tower's remarks suggest that Congress will be sympathetic to voting more money for missile defense when Reagan decides where and how to base the MX. He is expected to announce his choice by December. The leading deployment scheme calls for putting the MX missiles close together in what is called the "dense pack" formation.

Tower said the president telephoned him yesterday to congratulate him for steering though the conference a defense bill authorizing $178 billion for fiscal 1983. That is $5.4 billion less than what Reagan sought in February but is more than what several congressional critics say is justified for defense, particularly in light of the huge federal deficit.

A move is under way in the Senate to recommit the compromise authorization bill today when it reaches the floor on grounds that it provides for too much money for the wrong weapons.

There are also widespread predictions in Congress that the compromise authorization bill will require appropriations committees to cut much more deeply into Pentagon requests in order to stay beneath budget ceilings established by House and Senate resolutions.

Tower said Reagan had expressed pleasure that the administration got "most of the big-ticket items," including the MX, two aircraft carriers, the Army AH64 Apache helicopter and tactical aircraft. Reagan failed to get $54 million to start producing nerve gas.

On Friday, the conferees reversed their decision to ignore the will of the full House and restore funding for production of the gas. The conferees had quickly agreed just the previous day that Reagan should get the $54 million to produce nerve gas shells, called binary munitions.

But as they saw that their compromise bill would not only bust the limits set in the congressional budget resolutions, especially on spending, but would also shoot down the A10 attack planes championed by Rep. Joseph P. Addabbo (D-N.Y.), several conferees warned of a political blunder.

Addabbo, chairman of the House defense appropriations subcommittee, has been decrying the size of the Pentagon budget while fighting to keep the A10 in production. The plane is manufactured on his home ground on Long Island.

By putting together a coalition of anti-nerve gas, anti-budget-busting and pro-A10 representatives, several conferees argued in their secret sessions on the defense bill, Addabbo might get the House to reject the compromise measure when it comes up for approval on the House floor.

Several members bewailed the fact that The Washington Post had revealed Friday that the conference had restored the nerve-gas money, generating heat for the conferees.

Although restoring the money for the A10 might help win over Addabbo, Tower was adamantly opposed to this step. One reason, sources said, was his conviction that the AH64 Apache helicopter was much more urgently needed than the Air Force A10.

As the conferees assessed the political dynamics, they concluded that bowing to the House vote against nerve gas was the surest way to avoid seeing their version of the fiscal 1983 defense bill wind up in the House waste basket. The nerve gas and A10 funds were kept out of the bill that finally emerged.

Along with such coldly political calculations, participants said conferees also expressed highminded concern about whether the bill they were fashioning would buy the best kind of defense for the nation. One dramatic instance of that came as the conferees voted on whether to authorize money to build five MX missiles.

John W. Warner (R-Va.), chairman of the Senate Armed Services subcommittee on strategic and theater nuclear forces, though a staunch supporter of Reagan and his defense program, contended that authorizing production before the deployment scheme was chosen would be putting the cart before the horse.

However, he was on the losing side of the 11-to-7 vote authorizing MX production money.

As part of the attempt to offset increases made for the Apache helicopter and the Air Force MX, the conferees deleted one of two Trident missile submarines the Navy wanted to start building with fiscal 1983 money. Serious reservations also were expressed at this move, congressional participants said.