The Pentagon's research director predicted yesterday that an administration study panel will recommend increasing spending for missile defense by about $500 million between fiscal 1984 and 1985.

Richard D. DeLauer, at a breakfast meeting with reporters, said this would mean raising the current missile defense budget from $2.6 billion to "something over" $3 billion. He said a task force report making the case for such an increase will go to the White House in mid-June.

But DeLauer said that no missile defense could be totally effective if there were no restraints on offensive weapons. "This is why we need arms control," he said.

As undersecretary of defense for research and engineering, DeLauer said he will press for a broad look at various ways of stopping incoming warheads rather than zeroing in on a specific type of weapon. One example, he said, would be to perfect a way to focus laser beams on fast moving objects and then use the technique in a wide range of anti-ballistic-missile (ABM) weaponry.

Even under an accelerated research effort, DeLauer warned that it would be at least four or five years before the government could make an informed judgment about whether an effective missile defense was feasible.

White House officials, in briefing reporters on President Reagan's "Star Wars" speech in March, estimated that the pursuit of an ABM defense would cost about $1 billion a year. Pentagon officials said DeLauer was counting additional missile-defense elements in arriving at his estimate of $2.6 billion for current spending.

DeLauer also warned that the Soviets were upgrading the accuracy and explosive power of their older surface-to-surface missiles--the SS21, SS22 and SS23--to the point where they threaten to wipe out NATO warplanes dispersed around European airfields. He lamented the fact that the West is doing little work on aircraft that could jet off the ground before the missiles could catch them.

Another frustration, DeLauer continued, was the slowness of the U.S. military services in tailoring their war-fighting concepts to the precision weaponry now at their disposal.