A decade ago, had an American ambassador attended a meeting of the World Anti-Communist League, he probably would have been greeted with the same enthusiasm as Moshe Dayan at an Israeli Bonds dinner. There would have been smiles, applause and calls for the obligatory spech.

Last week, however, when U.S. Ambassador Robert E. White made a surprise appearance at the opening session of the League's 12th annual congress, it was as if Dayan had walked into a conference of the Palestine Liberation Organization.

"They didn't quite know what to do with me," White said afterwards, recalling his trip into the ultra-conservative lion's den, where the Carter administration's foreign policy is about as popular as that of the Kremlin.

Among those at this year's conference were former Nazi SS officers, two neo-Fascists from Italy reportedly wanted for terrorist acts, members of Alpha 66, a right-wing Cuban exile group, and Pedro Ibanez Ojeda, who attended as Chilean President Augusto Pinochet's personal envoy.

When Frederick Guirma, the delegate from Upper Volta, gave a speech urging the League to support blacks in South Africa, Rhodesia and Namibia, who he said "are fighting for their rights," there was dead silence.

The League later passed a resolution stating that South Africa is "beset by communist subversion" and that journalists who write about that country's policy of racial separation in a negative manner are "at the service of Marxism and its campaign of psychological aggression."

What became quite clear during the conference was that the Anti-Communist League supports any government, no matter how repressive or racist, that says it is anti-communist. The Carter administration's human rights policy is seen as nothing more than playing into the hands of the international communist conspiracy-as was the U.S. decision to recognize Peking.

"If the United States had a strong, pro-capitalist foreign policy, quite naturally many nations would strengthen their ties with the U.S.," said Bruce Larsen, head of the New Zealand delegation.

Larsen said he believed in democracy. When asked if he considered Paraguay, generally classified as Latin America's most authoritarian dictatorship, a democracy he said. "Certainly, it is. I do not believe in democracy for subversive leftist elements."

The League is particularly secretive about its own inner workings, about how many members it has and where its money comes from.

There were about 400 delegates from 86 countries at this year's conference, several of whom admitted that they had not paid their own way and most of whom refused to discuss the League or their presence.

Diplomatic observers said some delegates told them that all of their expenses were paid for, probably by the Paraguyan government.

The conference's most exciting moment came during the final session, when the debate over where to hold the next congress brought into the open a simmering internal dispute that some observers said could change the very nature of the League.

Until now, according to these observers, the League has been pretty much dominated by the Nationalist Chinese, who founded it. Taiwan's hope was to draw into the organization any anti-communist group that supported it in its diplomatic struggle with Peking.

According to the observers, however, one faction within the Saudi royal family has been pumping money into the League with the aim of capturing control and turning it against Israel.

At least one of the working groups at this year's conference passed a resolution supporting the Palestinians and condemning "Zionist expansionism in the Middle East."

Asked why the League was supporting the Palestinians, who have close ties with the Soviet Union, over the Israelis, who have close ties with many of the governments which the League supports, such as South Africa and Chile, Sam G. Dickson, an Atlanta lawyer who was a U.S. delegate, said "Israel has made herself repugnant to most nations of the world.

"Occasionally, one has to decide that the enemy of mine enemy is not my friend," Dickson said.