Senate Minority Leader Robert J. Dole (R-Kan.) said yesterday that the United States should supplement pending peace negotiations among five Central American nations by holding separate talks with Nicaragua's leftist Sandinista government and by making clear that Washington will not abandon the Nicaraguan contras.

Proposing "five points for peace," Dole said he hopes that the plan adopted last week by Nicaragua, Costa Rica, El Salvador, Honduras and Guatemala "can be one step on the road to peace in Central America."

He said he agrees with President Reagan that the plan "deserves a chance."

However, Dole, expected to be a candidate for the Republican presidential nomination next year, said he is "skeptical about some provisions and omissions" in the Central American initiative. Therefore, he said, the Reagan administration should take separate steps to ensure that U.S. interests in the region are safeguarded.

He announced that beginning Aug. 30, he and the three Republican members of the Senate's observer group for the Central American talks -- John S. McCain III (Ariz.), Thad Cochran (Miss.) and Steve Symms (Idaho) -- will visit the region to assess the situation.

His five points call for:Giving the peace process every chance, while bearing in mind that "good faith is a two-way street, and so far I see little to convince me the Sandinistas will respond in kind." Addressing the Central American plan's failure to specify that Soviet and Cuban assistance for Nicaragua's military buildup must be ended. "Unless that problem is taken care of, there is no settlement for us; there will be no long-term peace," he said. Insisting that the contras be included in any negotiations and be a party "to both cease-fire arrangements and post-cease-fire political activities inside Nicaragua." He said, "We just can't abandon the contras. American credibility can't stand one more trip down that disastrous road." Noting that the contras' $100 million in U.S. military aid expires Sept. 30, he called on Congress to vote new contra aid as the peace process advances. He said that if the plan brings peace, the unused funds could be put back in the Treasury, but the president should be given standby authority to keep aiding the contras if the Sandinistas prove to be "blocking or stalling an agreement." Holding direct U.S. talks with the Sandinistas, "not instead of, but as adjuncts to the Central American talks in two separate but related negotiations."

Secretary of State George P. Shultz has rejected Nicaraguan President Daniel Ortega's call for direct talks about the region. But Dole said, "Seeing Daniel Ortega trying to make this a big issue strikes me as totally phony. The question is not whether we talk to the Sandinistas but whether they are willing to talk seriously about matters that concern us."