One day after killing the Army's $5 billion Divad program, Defense Secretary Caspar W. Weinberger called for getting President Reagan's rearmament program back on track through increased military spending.

"We cannot afford a zero-growth defense budget again in 1987 and 1988, as we will have in 1986," Weinberger told the American Legion convention in New Orleans yesterday. "Our defense recovery is in the home stretch. We cannot quit now."

Weinberger's speech, released by the Pentagon, signaled that his cancellation of the Divad (for Division Air Defense) antiaircraft gun does not mean he will accept a flattening of the military buildup to help reduce federal deficits estimated at $200 billion or more.

"Up to this year," Weinberger told his audience, Congress "gave the president and me 95 percent of our defense recommendations." But the defense authorization bill pending before Congress puts the spending level nearly 5 percent below that projected by President Carter for fiscal 1986, Weinberger said.

Before the August recess, House-Senate conferees agreed on a compromise bill authorizing $302 billion for defense in fiscal 1986, an amount equal to last year's total plus an adjustment for inflation. This "zero growth" compares with the 5.9 percent after-inflation increase sought by Reagan.

The House had frozen the Pentagon authorization at $292 billion, with no increase for inflation. The Senate approved its own higher number in voting for the conference bill, but so many House members protested their conferees' acceptance of the Senate total that the House leadership postponed a vote on the compromise until after the recess.

On a separate track, the House and the Senate in their budget resolution have agreed on zero growth plus inflation for defense in fiscal 1986 and 3 percent real growth in fiscal years 1987 and 1988. It is these "out" years that Weinberger has now targeted for increases, as evidenced by his speech yesterday.

The big question is whether Reagan will ally himself with Weinberger or his White House budget advisers and Republican leaders in next year's battle of the defense budget. This year Reagan went along with a compromise worked out by Senate Majority Leader Robert J. Dole (R-Kan.).

Weinberger lost another round when the House and the Senate directed him in the defense authorization to cut $2.9 billion from the military retirement program and to restructure it. He indicated yesterday that he would bow to the inevitable and change the system for those entering the military but would fight to keep benefits intact for those already on active duty or retired.

In touching on foreign affairs, Weinberger assailed Soviet expansionism and said that Reagan "will not let our back be put to the wall in Nicaragua."