Agonizing negotiations climaxed today in agreement on a Basque home rule bill that could bring peace to Spain's northern provinces, where secessionist violence has caused more than 70 deaths this year.

Premier Adolfo Suarez and other political leaders hope the provision of a large measure of home rule will undercut popular support for the Baque guerilla organization ETA, which has waged a violent pro-independence campaign for 10 years.

Today's accord came after Suarez dispatched a plane to the Basque city of Pamplona to bring nationalist leader Carlos Garaichoechea to Madrid for resolution of last-minute differences.

Josu Elorriaga, a Basque nationalist congressman for Bibao and a member of the negotiating team, said: "The home rule bill will not immediately put an end to violence, but had agreement not been reached between us and the Madrid government, there would have been no possible peaceful solution."

For the past week, representatives of Squarez' ruling Democratic Center Party and the Basque Nationalist Party have held night-long sessions. Passage of the bill by the full parliament is consideredcertain, although details on the conditions of today's accord were not immediately available.

Government sources said that the accord came when the Basque negotiators accepted the principle that the Madrid government would be given the last word on the most divisive issues: control the police, judiciary, education and social services in the three provinces.

"ETA will now have to define a new strategy," congressman Elorriaga said. "Up to now they have fought against the central administration. From now on they will have to deal with a Basque administration. The undoubted support they enjoy at present will fall off."

The police question was, according to the sources, the most difficult of all. Frequent shootouts between police and ETA gunners and heavy-handed repression over the years have led to a serious breakdown of police-civilian relations and demands by extreme nationalists that the police be withdrawn from the area.

The sources said the present para-military police force in the Basque region - which numbers some 13,000 men - would be replaced gradually by Basque police units, with the Spanish Army having a major say in their recruitment and training.

A potentially explosive issue concerning the disputed ancient province of Navarre, bordering the Basque country, presented less difficulties than expected. Navarre is claimed as an integral part of the Basque country by the Basque nationalists, although only half the province is ethnically Basque. The other half strongly resists what it terms "Basque expansionism."

The Navarre issue was shelved during the negotiations pending further talks and a future referendum within the province. The remaining Basque provinces, Vizcaya, centered on the industrial port of Bilbao, Guipuzcoa, with its capital of San Sebastian near the French border and the inland province of Alava - comprising in all a population of 1.5 million will hold a referendum on the home rule bill in October.

Both the Basque Nationalist Party, which is politically moderate although staunchly in favor or home rule, and the Madrid administration fear initial further violence from ETA as the terms of the bill are made public.

ETA has throughout rejected the home rule proposals and fought for the creation of an independent left-wing state. ETA's political front polled 16 percent of the vote in San Sebastian in the March 1 general elections, a startling result that pointed to growing support for the secessionists. CAPTION: Map, no caption, By Dave Cook - The Washington Post