Managua, Nicaragua — The United States and Nicaragua are talking again.
As part of a new plan to smooth differences with the Sandinista leadership here, the Reagan administration has told top Nicaraguan officials that it will consider resuming economic aid if the Sandinistas will stop supplying Salvadoran guerrillas.
The offer, made as part of an eight-point proposal and delivered to the Nicaraguans April 8, could open the door to serious negotiations between the two governments.
It is, of course, a limited step at best. But the meeting last week of US Ambassador Anthony Quainton and top Nicaraguan Foreign Ministry officials could be the first in a round of talks leading to a lessening of US-Nicaraguan tensions--and Central American tensions as well.
It is clear that Washington is searching for ways to do just that. The Quainton session with the Nicaraguans came immediately after he had flown to Washington for a quick review of US-Nicaraguan relations. He did most of the talking in the course of the one-hour and 15-minute meeting, but the Nicaraguans were able to get their worries on the table as well. And high Nicaraguan officials indicate that this initial exploratory session should be followed by further meetings and that ''negoatiations between our two governments are likely.''
The eight points in the US proposal for improved relations include:
* A halt to Nicaragua's alleged support for neighboring rebels. El Salvador guerrillas are not spelled out specifically, but that is the implication.
* Prosecution by the US of anyone who plans or launches an invasion of another country from US soil. This would cover the Nicaraguan exiles who are training in south Florida.
* A US-Nicaraguan pledge of noninterference in the affairs of other countries in Central America.
* A ban on the import of heavy offensive arms into the region, a point that would cover the military buildup in Nicaragua. It is also proposed that there be a reduction of the number of foreign military advisers--again a point aimed at Nicaragua. Some 500 Cuban military advisers are thought to be on the scene there, in comparison with the 49 US ''trainers'' in El Salvador.
In addition, Washington suggests the Sandinistas repledge themselves to the political pluralism, mixed economy, and nonalliance that were part of their original goals when they came to power in July 1979.
Mr. Quainton met with Foreign Ministry officials Julio Lopez and Victor Hugo Tinoco, in the absence of Foreign Minister Miguel d'Escoto Brockman. Mr. d'Escoto is due back in the country by midweek and is likely to be present when they meet again this week.
The Quainton talks were the first substantive session between US and Nicaraguan officials since last October. There is no indication how the Nicaraguans will respond to the US proposal, but there is no doubt here that many within the Nicaraguan leadership want some new accommodation with Washington.
Leaders here are deeply concerned about the threat of US action and the buildup of anti-Nicaraguan forces in neighboring Honduras. They worry about the increasing frequency of military incursion from that northern country. This past week at least seven such raids have been reported in the local press.
The Nicaraguans also are concerned about the training of Nicaraguan exiles in Florida.