California Gov. Edmund G. (Jerry) Brown Jr., in another attempt to set himself apart from two Democratic presidential opponents, yesterday called for gasoline rationing using coupons.

"We're not going to fight the energy war with a popgun," Brown told the Women's National Democratic Club here. "We're going to have go make auto companies build more efficient cars and do it faster. We're going to have to adopt a program of coupon rationing."

At the same time, Brown tried to defuse any polical liabilities resulting from his support of gay rights by claiming that his position on the issue is no different than those of President Carter and Sen. Edward M. Kennedy (D-Mass.).

Asked if his presidential hopes would be hurt by his support of the gay rights movement, voiced at a rally here Tuesday night, Brown replied:

"I have no idea. But I see that the other two candidates, Sen. Kennedy as well as President Carter, sent representatives to express essentailly the same concept.

"So, whether it's indirectly or directly, the three candidates of the Democratic Party have come out for gay rights. I think that's good, and I think that drives the dialogue even further. I'm all for it."

Brown's position on the issue is different than those of the Carter and Kennedy representatives at Tuesday's rally.

A letter signed by Kennedy and distributed at the meeting said only "we must all be concerned" when people are discriminated against because of the sexual preference. A Carter spokesman said only that the White House has been open to meetings with gays.

Brown said that if he were president he would issue an executive order banning discrimination against homosexuals in federal employment, and that he would work for passage of gay rights legislation and appoint qualified gays to federal jobs.

Brown, who later left on a campaign trip to Iowa, also stepped up efforts to be included in a Carter-Kennedy debate, set for January in Iowa, with an attack on the Des Moines Register, which is sponsoring the event.

The paper's editors have not included Brown in the debate because his aides indicated he wouldn't contest the Iowa precinct caucuses, the first formal test of the 1980 race. Brown first campaigned in the state last week.

Brown said yesterday that he is shifting his campaign strategy to include Iowa and Minnesota as well as the early New England primary states as the "key tests" in his effort to win the Democratic nomination.

Claiming that Kennedy and Carter agree on most issues, Brown said, "I see my campaign as a definite alternative [and] a very realistic one.

"The Register has apparently determined that the people of Iowa, and of the entire nation, should view a debate between only two of the three Democratic candidates," Brown said in a statement.

On gas rationing, Brown said, "It is well to postpone the day of reckoning, but I believe that it's already come."