A Reagan administration would insist on increasing defense spending by, more than 7 percent a year after allowing for inflation, William Van Cleave, Ronald Reagan's military policy adviser, said yesterday.

Resident Carter, after first trying to hold annual growth in the Pentagon budget at 3 percent after inflation, is now backing a 5 percent yearly increase.

After declaring that Carter would not achieve that 5 percent objective because of reductions already made and in the works, Van Cleave said: "Even 7 percent is not enough." But he did not specify how much of an increase would be enough.

In discussing the pending arms control treaty called SALT II, Van Cleave said that it should be amended to cover long-range bombers deployed by both the United States and the Soviet Union rather than exempt the Soviet Backfire bomber as is now the case; count as strategic weapons to be limited all cruise missiles with ranges of over 100 kilometers; include the Soviet SS20 medium-range missiles now targeted on NATO, and count as strategic weapons all those produced, not just those on launchers as at present.

Asked how the Soviets could be persuaded to accept such a revamping of the arms control treaty already signed, Van Cleave said they must be shown that the United States is serious about an equitable agreement. SALT is on the wrong track, he said.

Van Cleave appeared on a panel along with David Aaron, a White House national security aide, and Alton Frye, foreign policy adviser to John Anderson, running as an independent for the presidency. The discussion was sponsored by the Arms Control Association.

Aaron said none of the steps Reagan has recommended for beefing up the nation's strategic forces are prohibited by the pending SALT II except for building an antiballistic missile defense. This raises the question, said Aaron in referring to Reagan, of "what will he do that we are not doing now?"