The Nicaraguan government, in the face of intensified troubles at home and abroad, is pursuing the U.S. offer of negotiations with surprising and uncharacteristic urgency.

Nicaragua's urgency is in contrast with its more relaxed pace in considering some of the same U.S. ideas during a then-secret dialogue last fall. At that time, Washington repeatedly prodded Managua for reactions to its messages--as the Nicaraguans are doing now to the Americans.

Foreign Minister Miguel d'Escoto said a principal change since last fall has been "the degree of hostility and the degree of aggression against our country" on the part of the United States. Last fall, he said, while expecting Reagan administration officials to be hostile toward Nicaragua, "we didn't feel they had already made a political decision to overthrow our government by direct or indirect means, overt or covert action."

Since then, d'Escoto said, there were "indications" that the administration has moved further, with reported acceptance by President Reagan of a $19 million CIA undercover plan against Nicaragua, stepped-up presence of U.S. warships in surrounding waters and U.S. reconnaissance airplanes overhead.

The Sandinista regime was quick to approve the proposal by Mexican President Jose Lopez Portillo, made in a speech here two months ago, for Central American diplomatic settlements involving the United States and nations of the region. After the Reagan administration followed up April 8 with an eight-point proposal for a U.S.-Nicaraguan accord, Managua quickened the pace of its expressions of interest.

On April 14, Nicaragua said it was willing to discuss the U.S. points and it presented 13 counterproposals as subjects for negotiations. On close examination, the counterproposals were repetitions of positions made public at the United Nations late last month by Nicaraguan head of state Daniel Ortega, with intriguing omissions and additions regarding the guerrilla war in El Salvador and an international economic squeeze here.

When the United States did not immediately respond, the Nicaraguan Foreign Ministry called in U.S. Ambassador Anthony C. Quainton April 17 and again April 20 to urge quick agreement on the start of negotiations, proposing Mexico as the site and the Mexican government as "moderator."

According to d'Escoto, Nicaragua expressed concern that Washington may be backing away from high-level negotiations, seeking to settle instead for less conclusive discussions through ambassadors in the two capitals. "The slowness of Washington to respond may signify they are having second thoughts," said d'Escoto.

Washington officials "say they are in no hurry, whereas we are in a hurry--we need to have the situation normalized so we can get on with our national tasks," said a Sandinista foreign-policy maker, who asked not to be quoted by name. This official charged it is increasingly evident that Washington is not serious about a negotiated settlement but has decided to use the maneuvers as "an international public relations effort."

Managua's 13 points, as conveyed to the State Department in Washington April 14, include demands for a halt of what was described as CIA financing of anti-Nicaraguan forces, a call to stop the patrols of U.S. warships near Nicaragua and to cease overflights.

In a turnaround of U.S. demands that Nicaragua halt alleged arms deliveries to Salvadoran guerrillas and use of Nicaraguan territory as a base for those guerrilla operations, Managua demanded that Washington stop the use of next-door Honduras "as a base for armed aggressions and terrorist operations" against Nicaragua and stop "the traffic in arms and counterrevolutionaries" with Honduras.

Those same demands had been made earlier by Ortega before the U.N. Security Council March 25 in advancing a resolution that Washington vetoed. Before the Security Council, Ortega also listed among his points the willingness of the Salvadoran insurgent leaders, political and military, to negotiate a settlement of the Salvadoran civil war. There was no mention of these negotiations, or of El Salvador at all, in the April 14 message to Washington. Nicaraguan officials said negotiations in El Salvador seem less likely since the election victory of right-wing forces there.

Another change from the Ortega speech was the addition of a new Nicaraguan demand, that the United States renounce policies designed to impose an "economic, financial or commercial blockade" against Nicaragua. This reflects a Nicaraguan charge that the United States has been pressuring its allies not to provide aid or trade to this country, whose economic situation has worsened.

Nicaragua's exports, mostly of food, coffee and cotton, have diminished. Inflation has been rising, contributing to a notable increase in complaints about the Sandinista regime from Nicaraguans disappointed with developments since the 1979 revolution.

"This is the most critical moment in the last 2 1/2 years, without any doubt," said Xavier Gorostiaga, director of the Institute of Social and Economic Study here, a former planner in the Sandinista government and generally a friend of the regime. Gorostiaga said he did not think the regime is in danger of collapsing but that a combination of "external threat, economic boycott and internal problems" poses a very serious challenge to the leadership.

At the top of most people's list of major internal developments was the denunciation of the Sandinista leaders April 15 by perhaps the most famous and popular revolutionary military figure, Eden Pastora, speaking at a press conference in Costa Rica. The government has mounted a series of television rebuttals and presented a former Pastora associate, Jose Valdivia, to suggest that the famous "Commander Zero" is selling out to the United States.

A Sandinista source called Pastora "the latest card" of the Reagan adminstration and said he is "a clay god" who has no recourse now except to join with the remnants of the deposed Somoza regime, which Pastora fought.

However, ordinary citizens brought up Pastora's name, not disapprovingly, in conversations about the current scene in Nicaragua.