Two Harvard professors have agreed to serve as policy advisers to Republican presidential candidate Ronald Reagan, campaign officials said yesterday.

Nathan I. Glazer, professor of Education, and Richard Pipes, Baird Jr. Professor of History, were among a list of about 60 experts selected to advise Reagan on matters of domestic and foreign policy and national security.

Pipes, a specialist in Soviet history and foreign policy, said yesterday he will advise the Reagan camp on U.S. -Soviet relations and other foreign policy issues.

Pipes criticized the Carter administrations's defense and foreign policies, calling them "unreliable and irresponsible."

Ultimata

He blamed the administrations's strategies for "getting us into the extremely difficult position of issuing ultimata which we cannot back up."

Pipes added that he would advise Reagan to "engage in a massive reinforcement and rebuilding of our military forces so that they can be called into play if we are threatened again in the future."

The United States must either build up its armed forces or cease issuing threats it lacks the power to carry out, Pipes said, adding that President Carter's handling of the crises in Iran and Afghanistan had caused the United States to "lose all credibility with its allies."

If Elected...

Although he stopped short of officially endorsing Reagan for president, Pipes said he "would very definitely endorse Reagan" in an election between him and Carter. Pipes said he had not discussed seriously the possibility of accepting a position in Reagan's administration if the former California governor is elected.

The recently announced advisers were part of a group of scholars and other experts with experience in a variety of foreign and domestic policy areas whom the Reagan campaign considered for the post, Joe Holmes, director of communications for the Reagan organization, said yesterday.

"They were chosen because of their standing as leaders in their fields," not necessarily because of their political affiliations, Holmes added.

Glazer was unavailable for comment yesterday.