The House Assassinations Committee said yesterday that it will commission new ballistics tests that this month on the rifle bullet that killed Martin Luther King Jr.

Del. Walter E. Fauntroy (D-D.C.), head of the subcommittee investigating the King assassination, also said that committee lawyers will interview James Earl Ray next week in the Tennessee prison where he is serving a 99-year term for the 1968 murder.

FBI experts have said that tests after King's assassination were inconclusive. They said the bullet slug that killed King was so distorted it was impossible to say it came from the Remington rifle which was found nearby bearing Ray's fingerprints.

Chief committee counsel Richard A. Sprague and deputy Robert Lehner, who is directing the King investigation, plan to talk to Ray Monday or Tuesday in what Fauntroy said may be just "the first in a series of threshhold interviews."

Ray's new lawyer, Jack Kershaw of Nashville, who will be present, has been quoted as saying Ray's story is that he turned the rifle over to a mystery man named Raoul and was sent off on an errand before King was killed.

A member of the Justice Department task force that reviewed the case recently said this account differs markedly from earlier versions Ray has given.

The committee too custody of the rifle and the bullet last Friday and plans to have two separate tests conducted by independent experts rather than the FBI.

The American Civil Liberties Union, meanwhile, announced that it now "strongly supports a continuation of the assassinations inquiry" in light of its new rules of procedure. ACLU Washington director John H. F. Shattuck said the committee had previously "failed adequately to recognize the rights of witnesses" but its new rules "are sensitive to civil liberties concerns."