President Reagan said last night that he does not feel bound to keep defense spending for fiscal 1984 and 1985 within the limits of the budget resolution he endorsed and Congress adopted earlier this year.

"I reserve the right to have the flexibility with regard to individual programs" beyond fiscal 1983, he told reporters at his White House news conference.

For 1983, he said, "we settled on that and what the figures would be," including a $7.4 billion reduction in the national defense spending account. "I feel bound by the overall figures, the projected deficits and the projected overall cuts," he continued, while drawing a distinction between grand totals and components within them. "But I feel that I should have the flexibility to come forth with the 1984 budget to delegate that spending to programs based on what I feel the needs are."

For months there has been a fight over whether the president, in the interest of reducing future deficits and winning support for his other budget proposals, should scale back somewhat the large multi-year defense buildup he set in motion last year.

Even after Reagan seemed to agree to some reductions in the budget resolution, the military and administration conservatives pressed him not to renege on his original commitments, in his campaign and in office, to rearm the country.

Before his news conference, the president, through White House spokesman Larry Speakes, seemed to be trying to reassure conservatives that he was not backing off.

"The president reserves the right to determine military spending on a year-by-year basis," Speakes told reporters yesterday morning when asked if Reagan would adhere to the military spending reductions for fiscal 1984 and 1985 negotiated by White House and congressional leaders.

While that statement may have reassured conservatives, some congressional leaders, including Republicans, reacted as if the president had just put his thumb in their eyes.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said he felt "very keenly" that Reagan should stay within the defense spending limits Congress set in the 1983 budget resolution for fiscal 1984 and 1985. Speakes said Reagan felt bound only by the fiscal 1983 total.

Associates said Baker was much angrier in private that he sounded in public. "Just furious," was the way one described the majority leader's reaction.

Baker and other Republican leaders were said to feel that Reagan's notice that all bets were off for fiscal 1984 and 1985 defense spending would put the Pentagon's pending fiscal 1983 defense budget in fresh jeopardy as well as help rally opponents for assaults on the president's rearmament plan next year.

Chairman Mark O. Hatfield (R-Ore.) of the Senate Appropriations Committee said ignoring the 1984 and 1985 ceilings "would be such a complete breach of faith. It's so ill-timed. How many times do you keep marching down the field only to find the goal posts have been moved?"

Chairman Ted Stevens (R-Alaska) of the Senate Appropriations subcommittee on defense and Chairman Pete V. Domenici (R-N.M.) of the Senate Budget Committee also were portrayed as "hopping mad." The fiscal 1983 budget still must get through Stevens' subcommittee.

The White House statement, Domenici said, was "inappropriate. It seems unjustifiable, unreasonable. It makes matters very difficult up here."

He said what was at stake were spending cuts--not from year to year but from the original rising Reagan budgets--of $9.9 billion in fiscal 1984 and $13.3 billion in fiscal 1985, arrived at after exhaustive negotiations between White House and congressional leaders.

Reagan wanted $253.2 billion in spending for national defense for fiscal 1984; Congress approved $243.3 billion. Reagan wanted $292.3 billion for fiscal 1985 and Congress wanted $279 billion.

"The president is reneging on his agreement on defense spending with Congress," said Democratic Whip Alan Cranston of California in typifying reaction of critics in his party.