President Reagan pushed Congress yesterday to approve financial aid for the Nicaraguan counterrevolutionaries, saying "it may be our last opportunity to persuade the Sandinista government to negotiate with the contras."

White House spokesman Larry Speakes said Reagan made this statement yesterday morning to Republican congressional leaders, who emerged from the meeting expressing guarded optimism that a reduced aid package could win congressional approval.

Senate Majority Leader Robert J. Dole (R-Kan.) predicted that the Senate would approve a "humanitarian aid" package today providing $32 million for the contras over two years. House Minority Leader Robert H. Michel (R-Ill.) was more cautious about House prospects but said a recent visit to Moscow by Nicaraguan President Daniel Ortega "changed a great many minds on the Democratic side."

The House version would provide $27 million in aid through March 31, 1986, and an additional $2 million to help provide a negotiated peace in Central America.

The House has consistently rejected aid to the antigovernment rebels, with the latest turndown coming on April 25. Michel's proposal was planned for a Thursday vote, but House leaders said it could slip to next week because of procedural questions.

The administration-backed Senate bill, sponsored by Sam Nunn (D-Ga.) and Richard G. Lugar (R-Ind.), would funnel the aid through the Central Intelligence Agency while the Michel bill, designed to win Democratic support, would prevent the aid from being administered by either the CIA or the Defense Department.

Speakes denied a New York Times report that Reagan has dropped his insistence that the aid be channeled to the rebels through the CIA. He said the administration favored the Senate version.

An administration official said the president's hope is that both houses will pass versions of the aid package and that Senate-House conferees would agree to pass the aid through the CIA.

Sen. David F. Durenberger (R-Minn.), chairman of the Senate Select Committee on Intelligence, yesterday withdrew his opposition to CIA involvement with the contras. His opposition to the CIA role last November was instrumental in halting congressional aid to the contras, but Durenberger said the CIA is "getting more oversight" now that he and Rep. Lee H. Hamilton (D-Ind.) chair the congressional intelligence committees.

Durenberger said he urged Reagan at yesterday's leadership meeting to bring the presidents of the five Central American countries, including Nicaragua, to Washington for talks.

White House comments on Central America yesterday made no reference to this proposal, but instead accused the Sandinistas of increasing tensions in the region.

"We're seriously concerned at signs of increased aggressive behavior by the government of Nicaragua against its neighbors," Speakes said. "Its attacks on Costa Rican territory in recent days are particularly disturbing. Evidence now available indicates that elements of the armed forces of the Nicaraguan government conducted a deliberate and unrprovoked attack on a Costa Rican civil patrol May 31, wounding nine and killing at least two persons."

Speakes said that the administration was "hopeful" of winning the latest test in the House, and congressional opponents of the proposal acknowledged they would have a difficult time defeating the Michel proposal. However, the Democrats have prepared three amendments that would dilute it.

One would sharply reduce the amount of aid.

Another would leave intact the current prohibition against aid from U.S. intelligence agencies that could be used "directly or indirectly" to support military operations in Nicaragua. The Michel proposal would weaken this language, allowing the CIA to provide intelligence information to the contras.

The third amendment would delay aid to the contras for another six months to allow the Contadora nations -- Mexico, Panama, Colombia and Venezuela -- to work out a peace settlement.