Charging that United States companies which operate in South Africa "contradict our tradition of liberal democracy and justice," Sen. Paul Tsongas (D-Mass.) yesterday called upon students to demand that the University adopt a stronger divestiture policy.

Speaking before 20 students at an Institute of Politics group. Tsongas said, "Because Harvard is the major institution of learning in the nation, it assumes responsibilities to use its leverage against apartheid policies in South Africa."

"If Harvard does not take the high ground, it is effectively endorsing economic, social and political injustice in South Africa," Tsongas said, adding that he favors a gradual divestiture policy to give companies flexibility in promoting racial equality in that country.

Tsongas praised the Carter administration's policy concerning South Africa, saying, "our support of majority rule is a politically wise decision."

"Since the transfer of power is inevitable, the U.S. should start cooperating with the winning side," he said.

Tsongas criticized the United States' past policy of accomodating South Africa's apartheid regime, saying, "Our consistent pressure on the Botha government could actually preclude violent revolution."

Another speaker at the study group, Daniel Purnell, the head of a U.S. organization promoting racial equality in South Africa, also said he opposes investments in businesses "guilty of discrimination," but added that United States companies should not divest, but instead should "play a tactical role in alleviating social injustice."

American initiatives such as education and training centers for Blacks can influence other countries to follow this path and eradicate apartheid, Purnell said.

"Divesting U.S. holdings--which only amount to ten per cent of total foreign investments is a "toy argument," Purnell said, adding, "companies around the world will remain, regardless of our rhetoric."

"If a player leaves a game, he's no longer a player. We should be players," Purnell said.

Purnell, who helped draft the Sullivan Code--an equal employment policy which 142 of the 350 U.S. firms operating in South Africa comply with, said he thinks that 90 per cent of U.S. companies are committed to racial desegregation.