President Reagan, promising not to lose interest in key conservative social issues as he fights the nation's economic problems, said yesterday that he will renew pressure on Congress to allow prayer in schools, ban abortion on demand and create tuition tax credits.

According to administration officials, Reagan will propose the tuition credits as part of his State of the Union message to Congress Tuesday night. But he announced his intentions in his weekly radio address yesterday even as he was completing work on Tuesday's speech, according to presidential aides.

Reagan, working on the message after rejecting three draft versions, also watched the Washington Redskins' game against the Dallas Cowboys as he worked at Camp David, aides said.

"In a few days, I'll speak about the economic situation facing us," Reagan told his radio audience, "but I also want you to know we'll not ignore the moral essentials in the coming months."

Congress rejected last year the tuition tax credit proposal and constitutional amendments to ban abortions and permit prayer in schools. The tuition proposal was defeated after arguments that it was an attack on the nation's public school system, unfairly helped wealthy parents of private school students and possibly supported discriminatory private schools. Yesterday, Reagan addressed those arguments directly, saying:

"Today 5 million American kids attend private schools because of the emphasis on religious values and educational standards.

"The overwhelming majority of these schools are church-supported--Catholic, Protestant and Jewish. And the majority of students are from families earning less than $25,000.

"In many parochial schools, the majority of students are from minority neighborhoods.

"In addition to private tuition, these families also pay their share of taxes to fund the public schools.

"I think they're entitled to some relief since they're supporting two school systems and only using one."

Aides said the president is considering a tax credit plan that would allow federal aid to school districts to be offered to parents as cash vouchers that could be used to pay for educational programs at public or private schools.

He is also said to be studying a plan for Independent Education Accounts, which parents could use as tax-deferred accounts to save money for college tuition.

Reagan also vowed to push again for school prayer, saying, "No one must ever be forced or pressured to take part in any religious exercise, but neither should the government forbid religious practice. The public expression through prayer of our faith in God is a fundamental part of our American heritage and a privilege which should not be excluded from our schools."

The amendment proposed by the president would allow school districts to decide whether they want prayer allowed. Prayer is banned in public schools by a Supreme Court ruling.

In addition to promising to pursue the tax credits and prayer initiatives, Reagan affirmed his pledge to fight for an anti-abortion amendment.

Reagan noted that "many people" came here yesterday for an anti-abortion rally, and said:

"I, too, have always believed that God's greatest gift is human life and that we have a duty to protect the life of an unborn child. Until someone can prove the unborn child is not a life, shouldn't we give it the benefit of the doubt and assume it is?"