The government of Ronald Reagan was so worried that leftwing opposition to General Augusto Pinochet might erupt into open civil war that in 1986 the US government considered offering political asylum to the Chilean dictator.

Documents recently discovered in US archives reveal that a mission headed by US army general John Galvin went to Chile in 1986 to assess the growing street protest and guerrilla efforts to upend the unpopular Pinochet regime.

As the US began to understand the depth and passion of the opposition, fears of civil war forced Reagan officials to look for alternatives including, as one document stated, "An honorable departure for President [Pinochet], who would be received as a guest of our [US] government."

The documents, unearthed by Chilean journalist Loreto Daza at the US national archives and records administration in Maryland, detail high-level Reagan administration debates on policy options to ease Pinochet out of power.

"One of the possibilities was to offer him [Pinochet] asylum. It was an offer to travel to the United States and leave power," said Daza, who is also the head of the journalism faculty at the Universidad del Desarollo in Santiago.

While the US had openly pushed for a military coup to overthrow the elected government of socialist Salvador Allende, by the mid-1980s, Pinochet had become such a polarising figure that US officials feared his continuation in power might help the Chilean left regain public support, said Peter Kornbluh, author of The Pinochet File.

"An asset like Pinochet becomes a liability when he is no longer seen as capable of stopping the forces of the left and creating a stable economic climate," said Kornbluh. "Reagan admired Pinochet and wanted to go to Chile to personally thank him for 'saving Chile' and tell him [Pinochet] that 'it was time to go'," Kornbluh said, citing declassified White House records. "But George Shultz [then secretary of state] said absolutely not. Pinochet had too much blood on his hands."

Kornbluh said Pinochet's intransigence with even the most conservative democratic factions pushed him out of US favour and that by fall 1986, the US government had decided to help end the dictatorship and restore moderate civilian rule.

General Galvin, who was then commander in chief of the US Southern Command, then based in Panama, is also suspected of informing the Chileans in 1986 of a massive arms shipment from the Cuban government to the armed wing of the Communist party, a group known as the FPMR – Frente Patriótico Manuel Rodríguez.

The Cubans hoped that the social unrest against the dictatorship had reached a tipping point and that a two pronged attack from both armed-resistance groups and massive street protests would topple Pinochet's then-13 year reign.

The internment of thousands of pounds of rocket launchers, automatic rifles, grenades and ammunition had been coordinated by a massive clandestine operation that involved the weapons being buried along the coast in northern Chile. However, before the armed resistance was able to utilize the bulk of their weapons and launch their offensive, the Pinochet government swooped in, seized the weapons and arrested numerous activists. Some weapons from the cache had been distributed and were used in an unsuccessful assassination attempt against Pinochet in September 1986 in which several of his bodyguards were killed and he barely escaped.

As historians continue to sort out the legacy of US-Chilean dealings during the Pinochet dictatorship, street protests continued this week in Chile. Marches, shootings and a mysterious bombing marked the anniversary of the overthrow of Chilean president Salvador Allende on 11 September, 1973.

On Monday, a small bomb exploded at the Escuela Militar [Military School] metro stop. The bomb injured an estimated 14 civilians and provoked widespread fear. No group took responsibility and accusations have ranged from extreme right to far left, though police officials suspected a ring of anarchists thought to be behind another 200-plus bombings over the past decade in Santiago.

On the eve of the anniversary protestors armed with rocks and petrol bombs clashed with riot police, and at least one bus was set on fire.