Prime minister Adolfo Suarez, facing a potential crisis for Spanish democracy, today called off a tour of Central America and the United States to deal with friction between the government and the armed forces over the handling of Basque terrorism.

The postponement by Suarez of his nine-day trip, due to have started Wednesday, followed the assassinations by Basque separatists of three military officers, including a general, in the past week.

Accoring to reliable sources, the military high command has demanded that the armed forces take part in antiterrorist operations in the Basque region against the Basque Marxist organization ETA.

A series of meetings since the weekend between the prime minister, his security advisers and senior members of the high command ended in a stalemate, the sources said. The government's position was that any intervention by the military over the Basque issue would invalidate crucial political moves to solve the Basque "problem."

The military commanders of the Canary Islands, south Spain and southeastern Spain in recent days have questioned the government's ability to cope with the violence in the Basque provinces and criticized the breakdown of law and order wince democracy replaced the authoritarian rule of Gen. Francisco Franco, who died in 1975.

The sources said that in an eight-hour "tense" meeting on Sunday night attended by the prime minister, senior aides in charge of security and the heads of the three armed services, the military chiefs conveyed the intense dissatisfaction of certain high-ranking officers. The latter allegedly demanded that the political that the political front orgainizations of ETA be declared illegal and that the government bring forward the date for implementing a security operation, with Army participation, due to oversee a vital referendum on Basque home rule on Oct. 25.

Although the home-rule agreement grants sweeping powers of self-government to the Basque community, the seccessionists grouped in ETA bitterly oppose it because it enshrines the basic principle of the unity of Spain.

The target of the military anger is an electoral coalition called Herri Batasuna (People's Unity), which is made up of minor parties sympathetic to ETA and which has polled up to 25 percent of the vote in certain areas in recent general and municipal elections.

The sources said that the military had demanded the closure of Herri Batasuna's offices and that the referendum security operation, code-named "Operation Diana," be brought into immediate effect. Herri Batasuna, following ETA directives, has ordered supporters to abstain in the home rule referendum.

Military anger overflowed Sunday when the military governor of the Basque province of Guipuzcoa was shot to death.

Last night an estimated 5,000 rightists demonstrated in the center of Madrid in front of the Defense Ministry, shouting slogans against ETA and Basque home rule and calling on the Army to take power.

Since the weekend, rightist newspapers have printed editorials making thinly veiled calls on the armed forces to "save Spain" by intervening in politics.