President Carter, pledging to "stay true" to the ideals of Martin Luther King Jr., called today for enactment of legislation to make Jan. 15, the slain civil rights leader's birthday, a national holiday.

Speaking from the pulpit of the Ebenezer Baptist Church, the spiritual headquarters of King's 1960s civil rights movement, Carter promised to strengthen and enforce existing civil rights laws and to fulfill "the promise of justice" contained in those laws through "vigorous affirmative-action programs."

But the president said the country must do "more, much more" than this, while outside the small, modest church north of downtown Atlanta several hundred protesters demanded administration action on jobs, housing and health problems.

As the shouts of the protesters outside filtered into the church, Carter departed from his prepared text to address two of the most important foreign policy issues facing the administration.

He said that as soon as agreement with the Soviet Union is reached, he will submit a new strategic arms limitation treaty (SALT) accord to the Senate "as a treaty," laying to rest the periodic suggestions that the agreement would be submitted to Capitol Hill as an executive agreement.

An executive agreement would require a majority vote of the House and Senate for approval, while a treaty requires a two-thirds vote by the Senate for approval.

The president also said, in the strongest terms he has used to date, that he would "not hesitate" to invite Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin to another summit conference if necessary "to carry out the full terms of the Camp David [Middle East] peace accords."

Speaking to reporters at Dobbins Air Force Base outside Atlanta before his return to Washington, Carter noted that this week a State Department delegation will go to the Mideast in an attmept to break the current impasse in the peace negotiations. He said he expected this mission to make progress, but that a final agreement on an Egyptian-Israeli peace treaty will involve "basic political decisions that have to be made at the foreign-ministers level.

"And if that doesn't work," he added, "without further delay, we'll be willing to meet with both leaders."

These comments represented the first time Carter has voluntarily raised the possibility of a second Middle East summit conference, and appeared to amount to a personal appeal on his part to Sadat and Begin to break the impasse.

Carter spoke here today after accepting the eighth annual Martin Luther King Jr. Nonviolent Peace Award from the King Center for Social Change. Monday is the 5/th anniversary of King's birth and the president used the occasion to endorse the national holiday legislation, an issue he skirted both as governor of King's native state of Georgia and, until today, as president. Sens. Edward M. Kennedy (D-Mass.) and Birch Bayh (D-Ind.) have said they will co-sponsor a bill this week to make King's birthday a national holiday.

The president traveled here at a time when a number of black leaders are voicing fears that budget cuts in social welfare programs will hit hardest at blacks and the poor. His appearance also came just two days after he fired Bella Abzug as co-chairwoman of the National Advisory Committee for Women. Abzug, a former New York congresswoman, is a leader of feminist groups which frequently align with civil rights organizations in liberal causes.

Outside an Atlanta restaurant where he had luch with his family before the speech, Carter was asked if he had any regrets over firing Abzug. "No," he replied.

The disaffection of some blacks with the administration was evident from the protesters, who lined up across the street from the church and competed in their chants with a groups of anti-shah Iranian students.

Calling themselves the "Coalition to Save the Poor," the group, which included leaders of the Southern Christian Leadership Conference that King helped to found, accused the president of backing down on some of his campaign promises.

Inside the church, Jammed with about 800 people, including about 50 representatives of foreign nations, Carter ignored the protests and pledged to take civil rights goals into the area of economic opportunity.

"We must and we will do more, much more," he said. "It is not enough to have the right to sit at a lunch counter when you can't afford to buy a meal. A ghetto looks the same even when you are sitting at the front of a bus."

Emphasizing his commitment to human rights as "the soul of this country's foreign policy," the president also said:

"Only madmen today can believe that war is thesolution to anything. Just as Dr. King and Mahatma Gandhi knew that nonviolence was not the course of cowards, so our search for peace is a sign of strength and not weakenss. We will not purchase a peace that is merely surrender of our ideals and beliefs, and neither will we seek to force our values on others."

Carter was warmly received by his audience, which erupted in a standing ovation when he called for enactment of the King birthday legislation.

The award the president received from the King center cited his support for the Humphrey-Hawkins "full employment" legislation, his appointment of minority-group members to federal judgeships and other posts, and a number of foreign policy initiatives, including the Panama Canal treaties and the establishment of diplomatic relations with the People's Republic of China.