Reagan administration officials said Tuesday that a proposed Dugway laboratory is needed to defend soldiers from exotic Soviet germ weapons but Rep. Wayne Owens said such defense is impossible.

The comments came as three House committees Foreign Affairs, Armed Service and Interior joined forces for a 31/2-hour session about the proposed germ-warfare defense lab."We certainly have the responsibility to the soldier to protect him and her against those who would use biological weapons," said Thomas J. Welch, a deputy assistant defense secretary for chemical matters.

Welch added that the United States has no offensive biological warfare program and renounced such weaponry when the treaty was signed. The Dugway facility, he emphasized, is to develop defenses.

But Owens, D-Utah, who helped arrange the hearing, said the facility has "an alarming trail of unanswered questions." He said it is "potentially very dangerous" and suggested that rather than build it the United States might better work for a stronger treaty banning biological weapons.

Owens called the Army careless and irresponsible for suggesting the facility.

A "biological Ollie North," following his own ideological path, might set off a renegade germ-warfare offensive, Owens said. And, he argued, "defense is impossible" against such biological weapons an assertion that Welch and other government witnesses disagreed with.

"We may not achieve a complete defense," Welch said, "but we can do a great deal in the way of protecting our troops with masks and protective clothing and in developing vaccines."

Others defended the proposed lab.

Rep. Jim Leach, R-Iowa, said the current 1972 germ-warfare treaty lacks verification provisions and has been repeatedly breached by the Soviets and their surrogates.

The proposed facility was backed also by Roger Harrison, deputy assistant secretary of state; Richard E. Sanderson of the Environmental Protection

Agency; Lynn Hansen of the Arms Control and Disarmament Agency; and Michael Poling of the Interior Department.

It was opposed by Jay Jacobson, a professor of internal medicine at LDS Hospital in Salt Lake City; Jeremy Rifkin, president of Foundation on Economic Trends, an environmental organization; and Anthony Robbins, professor of public health at Boston University.

Owens concluded his questioning of the witnesses by arguing that the "real solution has to be negotiations. . . . The fact that (absolute) control (of biological weapons) is not possible should not deter us from trying."

Rep. Jim Hansen, R-Utah, a member of the Armed Services Committee, did not attend Tuesday's hearing. Hansen said he was busy with House floor action on the Military Authorization bill and had heard the testimony on Dugway before, at a hearing in Salt Lake City.