MANAGUA, Nicaragua (AP) _ U.S. ''blackmail'' has not ended just because Secretary of State George P. Shultz could not persuade Washington's Central American allies to condemn Nicaragua, the Sandinista newspaper said Tuesday.

Barricada said Monday's visit to Guatemala by Shultz ''means a new level of North American pressure and blackmail aimed at blocking the Central American peace process again.''

Shultz and the foreign ministers of Costa Rica, Guatemala, El Salvador and Honduras met in Guatemala City and issued a declaration calling for ''peace, democracy, security, social justice and economic development'' in Central America.

The United States had wanted a statement denouncing Nicaragua on grounds it had failed to comply with a Central American peace plan the five Central American presidents signed at a meeting in Guatemala on Aug. 7, 1987.

Guatemala and Costa Rica opposed a strong statement, saying it would harden the Sandinistas' position, and the final statement did not specifically mention Nicaragua. Shultz flew to Argentina Tuesday, the second stop on his nine-nation Latin American tour.

Honduras was angered by the soft stand taken by Costa Rica and Guatemala. President Jose Azcona Hoyo sent a sharp message to President Daniel Ortega of Nicaragua saying Honduras would never form alliances with ''represive and totalitarian'' governments.

A Honduran intelligence report, obtained by The Associated Press from Honduran military sources, describing Nicaragua as a military threat to the entire region.

Barring a U.S. invasion, Nicaragua will remain in the hands of the Sandinistas, the report said. It predicted the Sandinistas would not enact democratic reforms and would grow even closer to the Soviet Union.

Barricada, the official paper of the Sandinista National Liberation Front, said Shultz tried to pressure the four Central American nations into signing a ''virtual declaration of war'' against Nicaragua.

''Even though Shultz has failed in his primary goal of getting the Central American governments to sell out the promises of Esquipulas II, everyone in the region expects new pressures and blackmail when he returns from South America,'' Barricada said.

Esquipulas II is the name given the regional peace plan.

In line with the plan, the Sandinistas and Nicaraguan rebels, known as Contras, reached a cease-fire agreement in March. The peace talks have been stalled since June, however, and the Sandinistas have cracked down on internal dissent.

Shultz is to return to Central America on Monday and Tuesday before going to Ecuador for the Aug. 10 inauguration of President-elect Rodrigo Borja.

Ortega's office said Tuesday he had decided to attend Borja's inauguration. Ecuador broke diplomatic relations with Nicaragua in 1985 but is expected to re-establish them under Borja.

In Washington, State Department officials said there are no plans for a Shultz-Ortega meeting while both are in Ecuador. The Reagan administration 's position is that the Sandinistas should negotiate directly with the Contras.