Vice President Mondale met yesterday with former Chilean President Eduardo Frei, a political gesture that could have widespread repercussions in Latin America.

Frei, 66, is a leader of the Christian Democratic Party, which was outlawed in March after Chile's military rulers accused it of plotting against the government.

Informed sources said the decision to allow Frei to meet with Mondale and National Security Affairs Adviser Zbigniew Brzezinski was made by President Carter in the face of strong opposition from within the State Department.

Influential liberals, including the Rev. Theodore M. Hesburgh, president of Notre Dame University, Sen. Hubert H. Humphrey (D-Minn.) and Sol Linowitz, a Panama Canal negotiator, supported the meeting, a well-in-formed source said.

Opponents of the meeting reportedly feared that it would antagonize the rightist generals who rule Chile, and that they might retailiate against lower-level Christian Democrats or others.

Chile and other Latin military governments were already angry with the Carter administration for its criticism of human rights violations in the area.

Presidential press secretary Jody Powell said Mondale discussed with Frei "our government's fundamental commitment to human rights and its place in our foreign policy."

There was no immediate comment on the meeting from the Chilean embassy.

The meeting was first announced by the Washington Office on Latin America, a liberal, church-funded group based on Capitol Hill.

Frei was in the United States following a tour of Europe during which he met with Christian Democratic leaders from Italy and West Germany and the kings of Belgium and Spain.

Frei, 66, who has long been a favorite of the American diplomatic establishment, was elected president of Chile in 1964. U.S. congressional investigations nine years later documented U.S. spending of $3 million in a covert campaign to defeat Frei's main opponent, Salvador Allende, in the election. Frei and his party denied having accepted U.S. funds.

Allende, a Marxist, was elected president despite further covert efforts against him by the Central Intelligence Agency. Frei led the opposition to Allende and tacitly accepted the coup that overthrew him in 1973.

The Christian Democratic leader is the most important opposition political figure living in Chile and the greatest political threat to the government of Gen. Augusto Pinochet:

The meeting with Mondale is expected to boost Frei's political position in Chile.

Another Chilean exile, Clodomiro Almeyda, is scheduled to meet later this week with Under Secretary of State Warren Christopher.

Almeyda, exiled leader of Allende's Popular Unity coalition, told a group of reporters and congressional aides last week that the U.S. government should use its "influence in the business world" to discourage investment in Chile.