The Vatican, contradicting statements by President Reagan, said today that Pope John Paul II never has endorsed U.S. policies in Nicaragua.

A Vatican statement released today said that except for a speech to a group of U.S. senators who visited here last weekend, which did not mention Central America or Nicaragua, "there have been no other messages from the holy father."

The carefully worded statement said it was "useful" to "clarify" several points regarding Reagan's recent peace plan for Nicaragua. It cited a recent communique issued by the Roman Catholic bishops of Nicaragua that said that the pope's willingness to mediate between Nicaragua's Marxist government and U.S.-backed rebels fighting it "should not be interpreted as a political stand in favor of any party or ideology."

The president told a religious conference in Washington Tuesday that he had received a message from the pontiff "urging us to continue our efforts in Central America." Questioned the following day during a photo session with Algerian President Chadli Bendjedid, the president said the pope "has been most supportive of all our activities in Central America."

Today's 32-line comment by the Vatican followed another statement released in Washington by the papal ambassador there, Archbishop Pio Laghi, which stressed that the Holy See's position on the situation in Central America -- primarily support for a dialogue -- was well-known and excluded "the possibility of the pope's support or endorsement of any concrete plan dealing, in particular, with military aspects."

There was no comment on the Vatican statement from the U.S. Embassy in Rome. Church sources here speculated, however, that President Reagan's comment may have reflected a mistaken impression by some U.S. policy-makers that the pope's ongoing campaign against Latin American supporters of liberation theology, a doctrine that uses Marxist tools of social and economic analysis, was a sign that the pope agreed with U.S. policy toward the Marxist government of Nicaragua.

The president's reference to papal support was made at a time when he has asked Congress for $14 million in aid to Nicaraguan anti-Marxist rebels. Archbishop James Hickey of Washington told a congressional subcommittee the following day that Roman Catholic bishops in the United States oppose such assistance.

The Vatican statement released today by spokesman Joaquin Navarro revealed that President Reagan informed the pope about his Nicaraguan peace plan in a personal letter April 4. The plan calls for a cease-fire and negotiations but says the $14 million in requested aid would be spent for weapons if no agreement between the two sides was reached after two months.

At the same time the pope received the letter, the Vatican statement said, Robert C. McFarlane, the president's national security adviser, discussed the matter by phone with Cardinal Agostino Casaroli, the Vatican secretary of state.

At that point, the statement said, the Vatican officially contacted the Nicaraguan Bishops' Conference, which confirmed its earlier offers to mediate provided both sides in the Nicaraguan dispute understood that the church could not impose a dialogue on anyone and that its involvement should not be given a partisan interpretation.

The Vatican statement also said that on April 13 the pope received a delegation of Republican U.S. senators headed by Majority Leader Robert Dole (R-Kan.), who handed the pontiff a personal letter from the president. Dole later told reporters that the letter dealt with "the troubling situation in Central America and arms control talks in Geneva." The pope's speech to the senators did not mention Central America.