The World Council of Churches is under heavy attack for last week's $85,000 grant, to guerrilla forces in Rhodesia - a move which critics charge will heighten, rather than diminish, racial tensions in that country.

Attacks on the Council's controversial Program to Combat Racism, which in the last nine years has given nearly $1.5 million in grants to a variety of self-styled liberation organizations in southern Africa, is hardly new.

This time, however, the sharpest criticism is coming from some of the most steadfast defenders of both the Council and the program many of whom are torn between their dismay over the latest grant and their basic loyalty to the council and its goal of combating racism.

The program was launched nearly a decade ago when the churches sought to give concrete support for the council's resolutions opposing racial discrimination.

From the outset, the grants to groups in southern Africa dedicated to overturning white minority governments drew outraged protests. Although the grants were never more than a few thousand dollars, traditionalists both in and out of the church claimed that the churches were promoting bloodshed and revolution.

Defenders replied that the grants carried the stipulation that council funds could be sued only for humanitarian purposes such as medicine, welfare and education, and not for arms. They likened the black African groups to the underground in World War II Europe except that the villian in Africa was the white minority rule instead of nazism.

Yet, with the "internal settlement" in Rhodesia last March, some black leaders became part of the formerly all-white government of prime minister Ian Smith. It was no longer a clear case of black against white.

Feeling in church circles over the Rhodesian situation are heightened by the fact that two of the three black leaders who joined with Smith in March are not only churchmen but heroes within their respective denominations.

The Rev. Ndabanigi Sithole is a minister of the United Church of Christ who received his theological education at Andover Newton Theological School near Boston. Bishop Abel Muzorewa is head of the Methodist Church of Rhodesia, which is a product of missionary efforts in that country and an intergral part of the United Methodist Church in the United States. Muzorewa is a full-fledged member of the U.S. church's Council of Bishops.

Both men have frequently addressed gatherings of their churches in this country and are highly respected.

The Council decision, therefore, to support the guerrilla forces opposing the new biracial government was a bitter blow and, some American church leaders feel, a tactical disaster.

The giant to the guerrilla Patriotic Front "pits black against black," said Louis Miller, associate general secretary of the Methodists' world mission board.

By choosing one side in the controversy, she said, the council "is making a political statement" instead of the humanitarian action which the anti-racism program is chartered to be.

"It's going to hurt them," she predicted. "We've got people asking us to withdraw from the WCC."

Leaders of the United Church of Christ, a denomination known for it dedication to ecumenical ideal, has called for "a review" of the grant to the Patriotic Front.

"It is not obvious," says a carefully worded United Church position paper, that the grant "really serves very well the democratic goals of the World Council of Churches' Program to Combat Racism."

The United Church statement also criticizes the Council for failure to consult "the church constituency within Zimbabwe (Rhodesia) or elsewhere in the World Council of Churches family . . ."

The New York office of the World Council of Churches acknowledged that in addition to complaints from denominations about the grant, there has been a steady stream of complaints from individuals. "I imagine we'll be hearing about it for some time," a staff member said.

One of the points at issue is that the controversial grant was made by a four-person committee of council officers. While such an action is permissible under council rules, critics wondered why a decision in such a sensitive area was made by the handful of officers only six weeks before the meeting of the council's more representative Executive Committee.

Cynthia Wedel of Washington, one of the six presidents of the World Council of Churches, acknowledged that she was surprised by the announcement last week.

She speculated, however, that committee members "must have had some reason to feel it had to be decided then . . . that people were hungry, perhaps, and to wait might have been too late."

She said that "when you are working in an area as sensitive as this, you have to have a little bit of trust in the people delegated to make decisions. She added, "I have complete confidence in them."