Pope John Paul II appealed to Basque terrorists today to abandon violence as he delivered a sermon in the heart of the Basque country at Loyola, birthplace of St. Ignatius, the founder of the Jesuit order.

The Basque trip came on the sixth day of the pope's 10-day tour of Spain, the first to the country by a pontiff. It follows the assassination Thursday of Spain's top field general, Victor Lago Roman, 63, by members of ETA, the Marxist Basque separatist organization.

The pope's appeal, which came during an open-air mass conducted at the huge 18th century basilica dedicated to St. Ignatius, was framed in low-key, even gentle, terms.

Recalling the assassination attempt that seriously wounded him last year, the pope spoke earnestly and quietly to the young men of the Basque country: "I want to tell you with affection and with firmness, and my voice is that of one who has personally suffered violence, not to let your generosity and altruism be used."

The pope said, "Violence is not a way of building. It offends God, those who suffer it and those who practice it. Once more I repeat that Christianity understands and recognizes the noble and just struggle for justice at all its levels, but it forbids the search for solutions through the paths of hatred and death."

His appeal contrasted in tone with his impassioned plea to Irish Republican Army gunmen during a trip to Ireland in 1979. Then, John Paul, "on bended knee," urged an end to the killing in Northern Ireland.

The pope's short stopover in the Basque region was a nightmare for security officials. In a massive clampdown for the visit, police sealed all access to Loyola, a small community framed by forest-covered hills, hours before his arrival and, at the last minute, switched the timing and location of his helicopter landing.

Fears for the pope's security were also heightened after the shooting death of Gen. Lago. That assassination momentarily shattered the calm that had followed the landslide electoral win of the opposition Socialist Party in national elections Oct. 28.

Spanish analysts believe a major contributor to this calm has been the headline-dominating progress of John Paul through Spain. He arrived here Sunday and has been feted ever since by huge crowds. Millions have cheered him as he has spoken out against contraception and divorce among other issues that in a modern and secular-leaning Spanish society have ceased to be controversial.

The pope, displaying his celebrated charisma in a grueling schedule of rallies, church services and cross-country trips that force him to leave Madrid before light and return after nightfall, seems to have sparked a religious revival in a nation that was fast turning its back on what was once all-embracing Catholic influence and power.

Despite their landslide win, the Socialists appear set to rethink aspects of their program that clash with Catholic pressure groups, notably on the issue of public funding for religious schools.

In Loyola, where 150,000 were estimated to have attended the service after arriving overnight to avoid the security checkpoints, the reception followed the successful pattern set during the past days.

John Paul heightened the enthusiasm by praising the longstanding Catholic tradition of the Basque people and the importance of the Basque saints. His tribute to St. Ignatius was linked to that of another Basque Jesuit, St. Francis Xavier. The pope visited St. Francis Xavier's shrine, close to the city of Pamplona, after he left Loyola. He then traveled to Zaragoza.