President Carter endorsed yesterday a recent Supreme Court decision against federal funding of elective abortions.

He said that ruling and an earlier one, which together may end federal funding of Medicaid abortions for poor women except when their lives are threatened, are "reasonably fair" and should be strictly interpreted.

"As you know, there are many things in life that are not fair, that wealthy people can afford and poor people can't," the President said. "But I don't believe that the federal government should take action to try to make these opportunities exactly equal, particularly when there is a moral factor involved."

The comments, voiced during Carter's 11th televised news conference, brought an almost immediate wave of criticism from pro-abortion groups, who have argued that the government should try to give poor women the same options for coping with unwanted pregnancies that are available to wealthier women who can afford private abortions.

On June 29, the U.S. Supreme Court nullified a federal judge's ruling holding unconstitutional a congressional ban on federal funding of abortions to end pregnancies that do not endanger a mother's life. The judge had ruled it denied "the needy, the wards of the government . . . the means of exercise" a right guaranteed to those with money.

The Supreme Court sent the case back to U.S.District Judge John F.Dooling Jr. of Brooklyn "for further consideration in light of" a June 20 Supreme Court ruling that neither the Consttiution nor the Social Security Act required states to spend Medicaid funds for abortions they do not consider medically necessary.

Carter had new comments to make on a number of issues during his half-hour news conference. They included:

He does not think the monitoring of domestic telephone conversations by the Soviet Union or other nations is an act of aggression, "although it may be an intrusion into our security," and the United States is "taking adequate steps now to prevent its creating a threat to our country."

He doesn't yet know whether he will pick a new FBI director from the five names presented to him by his special search committee or whether he will choose someone else. Attorney General Griffin B. Bell disclosed Monday that both he and Carter have a sixth person in mind.

He feels "very good" about the U.S. economy. Despite "many areas of uncertainly," he is "impressed with the long-range trend projections that have been given to me."

He believes his energy proposals provide "an adequate incentive for production and exploration of new natural gas." Deregulation of natural gas prices, as called for by some Republican members of Congress, would cost consumers at least $70 billion more than his own proposals, he said, and would "be a gross overburden on the American people and it would not result in a substantial increase in production."

The Senate "made an improper decision" Monday when it refused, 49 to 38, to kill the nuclear fast breeder reactor at Clinch River, Tenn.

The Senate, which has passed a restriction limiting federal financing of abortions to those that are "medically necessary," and the House, which earlier passed a much stricter ban, are scheduled to go to conference soon to work out their differences.

Both versions of the ban are part of the more than $60 billion funding bill for the departments of Labor and Health, Education and Welfare. One source close to Carter said the President's comments should not be interpreted as meaning he has decided to vete the bill if its provisions for abortion funding do not coincide exactly with his own.

The criticism from pro-abortion groups included a statement from American Civil Liberties Union executive director Aryeh Neier that Carter's "attempt to impose his personal morality from the White House is a serious abuse of presidential power."

Neier said Carter "seems unconcerned that this broad policy statment of his personal views will jeopardize the life and health of millions of poor women."

"During his campaign Carter promised to be the President of all the people," Neier said. "In his statements on abortion, he has shown that he is President of the rich."

Yesterday the President publicly said for the first time that he thinks pregnancy as a result of rape or incest, as well as when a woman's life is threatened, should be exceptions to a general ban on federal financing of abortions.

"In my opinion the federal government being willing to finance abortions as it has been in recent months is an encouragement to abortion and its acceptance as a routine contraceptive means," Carter said.

"I know as well as anyone in the country . . . the intense feelings on both sides of the abortion issue. But my own personal feeling is that the Supreme Court rulings now are adequate and they are reasonably fair . . ."

On Soviet surveillance of domestic telephone conversations, Carter said interception by other nations "on a passive basis" has become common because many are transmitted by microwave.

The President said he didn't know the full circumstances involved, but his administration - and perhaps the Ford administration - have taken steps to make phone communications directly related to national security interception-proof.

"For instance, the lines going into and out of the Defense Department and my own office, we try to make sure that they are cables, they are buried underground, they are not subject to this electronics type of being overheard," he said.

A White House source said over the weekend that a classified report on the weekend that a classified report on the problem is being drafted for Carter. Sen. Daniel Patrick Moynihan (D-N.Y.) said Sunday that the Soviets are tapping telephones of "literally millions of telephone subscribers," and that Carter should demand that they stop.

On a future FBI director, Carter said he has met with two of the five recommended candidates so far, is scheduled to meet with two others this week, and will also interview the fifth before deciding whether to interview anyone else.

It has been reported that the sixth candidate is John A. Mintz, 41, a Georgia native who is the FBI's chief counsel. The Los Angeles Times reported that Mintz tied with two other candidates for sixth place when the nine-member selection committee voted on prospective candidates.

Carter said the government's contribution to a "general uncertainty" about future economic circumstances includes debate around the issues of energy, tax reform, and welfare reform.

He said Congress now understands "much more clearly" what he stands for, and that Congress still has some "hard questions to answer," including how to finance the Social Security system.

He said he disagrees with the decision of both houses to include funds for some of the water projects that has called "wasteful" in the public works money bill.

That bill, which also contains funds to keep alive the Clinch River breeder reactor, is on the verge of Senate passage.

Carter has asked that funds for the breeder reactor be cut off as part of his attempt to keep weapons-grade nuclear material from spreading to countries that do not now have access to it.