Image copyright InM/GETTY Image caption Mary Robinson, who was president of Ireland from 1990 to 1997, met Gerry Adams on a private visit to Belfast in 1993

Confidential UK state files from the early 1990s shed new light on how the granting of a US visa to Sinn Féin's Gerry Adams caused friction between the White House and the British Government.

They also show tense Anglo-Irish relations as Irish president Mary Robinson shook hands with Mr Adams in west Belfast.

This was a delicate point in the peace process before the 1994 IRA ceasefire.

Hundreds of state files from 25 years ago were released on Friday.

In the early 1990s, Northern Ireland was in the international spotlight as hopes grew of an end to violence.

Image copyright Getty Images Image caption John Hume and Bill Clinton at the White House on St Patrick's Day in 2000

With President Bill Clinton in the White House, the American administration began to take a more active role in the peace process, after many years of lobbying by SDLP leader John Hume.

Mr Adams was granted a 48-hour visa to travel to America in January 1994, in spite of sustained pressure from British officials to prevent it happening.

The papers show that the combined efforts of Downing Street, the Northern Ireland Office (NIO) and the UK Embassy in Washington could not stop it.

Mr Adams made a number of speeches and public appearances during his whistle-stop visit to New York, but was not allowed to fund-raise or travel to other cities.

IRA violence continued until August when a ceasefire was called.

'Private visit'

Throughout the early 1990s, Mr Adams was the centre of political attention.

The British Government's attitude was that until the IRA gave up violence, he should not be treated like a normal politician. He was even banned from talking on TV and radio.

The decision by Mary Robinson to meet him during a visit to Belfast in June 1993 did not go down well.

British officials made their feelings clear to Irish officials.

A note of the exchange from an NIO official stated: "The Irish were deeply embarrassed and realised that this was a disaster in the making, but they had no control over the president's visit which was a private one."

Image caption Albert Reynolds was the Irish prime minister between 1992 and 1994

The state papers also show concern at the frequency of visits to Northern Ireland by President Robinson and the then Taoiseach Albert Reynolds.

An NIO official talked about "applying some brakes" to the visits.

However, in a memo to the NIO, the UK ambassador in Dublin, David Blatherwick, defended Irish cross-border trips.

He wrote: "They convey a sense of normality and, of course, make Articles 2 and 3 look even emptier than they are."

The ambassador added: "Ten years ago I never expected to see an Irish minister attend a function in NI as a guest of the secretary of state.

"Dev must be spinning in his grave."