The Spanish government called on the Army today to participate actively for the first time in the struggle against Basque separatist terrorism.

The decision, reportedly in response to hard-line military pressure, was part of a new program to combat violence in the Basque country. It underlined the concern demonstrated by civilian leaders here to avoid alienating the conservative Spanish military since last month's coup attempt.

Reflecting that concern, King Juan Carlos called in the country's generals and admirals and warned them against any hasty actions that could engulf Spain in "real tragedies," an evident allusion to civil war between those eager to continue the transition to democracy and those, particularly in the military, who feel state authority is fading under post-Franco liberalization.

Within hours of the government's stepped-up security measures including the Army, there were reports of widespread arrests of Basque radicals among members of the political grouping Herri Batasuna, or People's Unity, which acts as a political front organization for the ETA gunmen. Police sources put the detentions at 26 but Basque radical sources spoke of nearly 100 arrests.

The executive decision to bring the military directly into antiterrorist operations was a reversal of previous government policy, which maintained that police and the paramilitary Civil Guard were sufficient to cope with the security threat posed by Basque separatists of the ETA organization.

Hard-line military pressure to take new steps against the separatists built up over the weekend after the murder by ETA gunmen of two Army colonels. Against that background, Juan Carlos alternately sweet-talked and chided the gathering of nearly 50 top officers from the three armed services at an unprecedented meeting at the royal palace in Madrid.

Referring to the dramatic events Feb. 23 when the parliament was stormed by insurgents and sectors of the Army wavered in their loyalties, the king congratulated the forces, saying he was "proud of the behavior."

"We overcame those serious moments precisely because of your discipline, serenity and good sense," the 43-year-old monarch told the assembled generals and admirals.

Juan Carlos then went on to warn the military against involvement in future plotting and hasty actions. Appealing for a strict observance of the laws and the constitution, he asked the service chiefs to "coldly analyze what can and what cannot be done in order to avoid condemning [Spain] to bloody confrontations and an isolation from the rest of the world."

The double-edged royal speech reflected the standoff between civilian and military power that has characterized political life in Spain since the coup attempt. The putsch failed and four generals, along with 24 other ranking officers, have been indicted on counts of military rebellion. But the government is purposely looking the other way at signs of far wider ramifications of the plot and refusing to pursue investigations any further.

At the same time, the armed forces have increased their influence and pressed for stern action against terrorism -- a demand that formed a main plant of the insurgent platform last month. Escalation of ETA actions prompted calls from the chiefs of staff for declaration of a state of emergency in the Basque country, according to informed Madrid political sources.

Prime Minister Leopoldo Calvo-Sotelo momentarily deflected the pressure and issued an antiterrorist plan that allows the military to patrol frontiers in the Basque country and involves the Army in a newly introduced joint command to combat terrorism. As part of the plan, the government also issued urgent instructions to the parliament to prepare legislation setting out the framework for a declaration of a state of emergency and a state of siege.