The United States took initial steps toward a dialogue with Nicaraguan guerrillas today in a secret meeting here between a Carter administration envoy and members of a guerrilla-backed provisional junta.

In a private late-night session, Carter envoy William Bowdler met with four of the five junta members, including Sandinista National Liberation Front leader Daniel Ortega Saavedra.

The meeting was the first direct contact between a high level U.S. official and the Sandinista leadership. Ortega is one of the founders of the guerrilla organization and is part of its national directorate.

Informed sources said that little came of the session, however. The sources said Bowdler made no mention of a new U.S. plan, privately proposed to President Anastasio Somoza early this week, to resolve the Nicaraguan crisis through a "constitutional" political program that ignores the provisional junta and seeks to limit Sandinista participation in a future government.

The left center "reconstruction junta" was announced two weeks ago to replace Somoza, whom the guerrillas are tyring to overthrow in a bloody civil war. Plans are for the junta to establish a capital in one of several Nicaraguan cities now held by the Sandinistas, and to request foreign recognition.

In a news conference here Wednesday, junta members Sergio Ramirez, Violeta Chamorro and Alfonso Robelo outlined plans for their administration, which foreign diplomats here described as "surprisingly moderate."

The junta proposed the formation of a 30-member legislative council under their executive authority that would include all of Nicaragua's political parties, union and civic federations and business groups - except those directly allied to Somoza. They said they hoped for early free elections following an unspecified period for reconstructing the destroyed economy.

The junta program concentrates heavily on development, full employment and agrarian reform. It calls for non-interference with privately owned property, again excepting that belonging to Somoza, who is variously estimated to own between one-third to two-thirds of all cultivated land in Nicaragua.

The junta said it expected to take power facing a national debt of approximately $1.3 billion, that it would need $80 million simply to feed and house the country for the rest of the year and that Nicaragua would seek extensive international assistance.

The three maintained that the Sandinistas would have only one vote in the junta - Ortega's - and that they expected to maintain only a "modest" armed force. "Honest" National Guard soldiers, they said, would be welcomed into the new army, while those charged with corruption, murder and other crimes against the people, including Somoza, would be turned over to an "institutionalized judicial system."

Foreign policy will be nonaligned, they said, and their government will seek open relations with all countries who "respect Nicaragua's sacred right to self-determination."

Informed for the first time this morning of the new U.S. plan, Ramirez, Chamorro and Robelo expressed anger at its existence and surprise that Bowdler did not inform them of it.

They charged the United States, in seeking to oust Somoza while avoiding what it considers a radical alternative, with trying to intervene in an internal situation it does not understand. They maintained that the Sandinistas have the overwhelming support of the Nicaraguan people and that any program that does not have Sandinista approval would only prolong the Nicaraguan civil war and result in more loss of life.

The three also noted that the junta now has the public backing of Nicaragua's largest business association and has been recognized by a coalition of moderate Nicaraguan political groups.

Ramirez, Chamorro and Robelo, who have taken refuge in Costa Rica since the Nicaraguan war began, arrived here yesterday on a state visit. Panama and Grenada are the only foreign countries that have recognized the junta as Nicaragua's legitimate government, although four other Latin American nations have broken relations with Somoza.

The fifth junta member, leftist union leader Moises Hasan Morales, is fighting behind guerilla barricades in Managua.

While the United States says it recognizes popular support for the Saninistas and does not seek to exclude them from a future Nicaraguan government, it believes the junta composition is too radical. The State Department has backed away from recent accusations of strong Cuban ties to the Sandinistas, but it apparently fears the installation of a Nicaraguan government is not in accord with U.S. interests.

[Chairman Edward Zorinsky (D-Neb.) of the Senate Foreign Relations Committee's subcommittee on Western Hemisphere affairs, labeled the current U.S. policy a self-deception and declared: "The Sandinistas will be victorious . . . We should welcome that victory and . . . move immediately to recognize the proposed provisional government."] CAPTION: Picture, Nicaraguan soldier fires behind a barricade in Managua Wednesday. UPI