Basque terrorists - in from the cold - vow to renounce violence

The automatic gates grind shut along the corridor leading to the special visiting room. This is Alcala-Meco, a high-security prison. It lies at the end of a country road which weaves through desolate wheat fields, 15 miles northeast of Madrid.

At the other side of the glass barrier sits Carlos Catalan Sanchez. He does not seem to fit the newspaper mug-shot image of a convicted terrorist.

A relaxed, smiling, college-graduate type in his early 30s, Mr. Catalan is looking forward to completing a journalism degree in two months. Almost one-third of the way through a 15-year-and-nine-month sentence for terrorist activities in the Basque separatist organization ETA, Mr. Catalan is 1 of 43 ETA prisoners who have signed a petition asking for pardon.

He is still reluctant to talk about the request for pardon, which initially was hotly contested by other Basque militants in the jail.

The unique feature of this Spanish attempt to bring terrorists in from the cold is that these people are being asked to do no more than pledge to give up arms. ''We totally disassociate ourselves from any armed organization and reject violence as a means of political action,'' the 43 prisoners say.

Both officials of the Socialist government and representatives of the prisoners emphasize there is no pressure put on them to collaborate with police against their former comrades - which would expose them to ruthless reprisals. Nor are they pressured to renounce their past or give up their campaign against centralized rule in the Basque country.

A spokesman for the Spanish government ombudsman, speaks of the process in terms of a ''conversion'' for many of the people involved.

The government views the potential indultos, or pardons, as a possible breakthrough in the fight against ETA's continued campaign of shooting, bombing, and kidnapping. In the past, the left-wing Basque nationalist party, Euskadiko Ezkerra, took the initiative to negotiate with the state for the rehabilitation of jailed ETA people. Under the previous centrist government it helped organize the return from exile in France of dozens of members of ETA's more moderate Politico-Militar faction.

All along, a key figure in the negotiations has been Mario Onaindia, the bearded, charismatic secretary-general for Euskadiko Ezkerra who, under Franco, was sentenced to death as one of the ringleaders of ETA.

Onaindia was freed under a general amnesty for political prisoners in October 1977 after democracy was restored. Although Basque extremists have been clamoring for another amnesty, such a measure is ruled out, since Spain's constitutional government does not acknowledge that there are political prisoners.

Onaindia's group has dug up an old liberal law dating back to 1870 which allows for individual pardons. One of the big questions is whether it can be applied to those convicted of murder. Only 1 of the current 43 petitioners has been convicted for a crime involving bloodshed. Despite the collective document, government officials take care to point out that each case will be studied individually.

''The Spanish state must be flexible and make way for a third possibility besides dying in the streets or staying in jail,'' says Onaindia. He means allowing ETA convicts to continue the ''fight'' politically. ''But for this, you must be able to get out of prison,'' he says.

Onaindia argues that the reason for violence disappeared with the end of Franco's dictatorship. Onaindia maintains that his own change of approach was a ''logical path'' to follow. But he rejects the label arrepentidos, or repenters, that has been attached to the convicts now seeking a pardon.

The hard-line ETA-Militar, which has rejected political means of pursuing its objectives, is nervous about the impact the pardons may have. This was shown last February when the affair was first publicly aired: An ETA commando cold-bloodedly shot Mikel Solaun, a former member who had returned to ordinary life, in front of his wife and daughter.

''The whole thing is a big gamble,'' says ETA convict Carlos Catalan.

It is a gamble for the government, too. ''We cannot risk having a failure,'' says Ramon Jauregui, the Madrid government's chief representative in the Basque country.

It is understood that the Spanish Army and police, which are the main victims of Basque terrorism and highly sensitive to the whole issue of Basque regional claims, have so far accepted the pardon process.

The government is hoping that the pardons will sap the morale of ETA. For one , it would reduce ETA's capacity to drum up solidarity for comrades in jail and also undermine the position of extreme Basque factions campaigning for a general amnesty. Although ETA's political front, the extremist party of Herri Batasuna, managed to maintain the support of 15 percent of the voters in the last regional elections, some observers see ETA's support as weakening.

Factors contributing to the wearing down of ETA include the factional disputes among the hard-core ETA-Militar, and the virtual disbanding of the Politico-Militar wing of ETA. A police expert recently commented: ''An 'army' that begins to tolerate desertions is an 'army' that's beginning to incubate the germ of defeat.''

Pro-ETA demonstrations no longer rally the numbers they once did, and popular outcry in the Basque country against the killings has grown.