Mr Cahill, who received his visa at 5am yesterday, arrived in New York from Dublin last night. A founder member of the Provisional IRA and a former commander of its Belfast brigade, his request for a visa was supported by the Irish government and finally granted after the personal intervention of President Clinton.
The British embassy did not formally protest in opposing the visa, the spokesman said. Earlier in the year London was rebuffed by the White House when it failed to stop the Sinn Fein leader Gerry Adams getting a visa.
Mr Cahill is likely to be influential among Provisional supporters in the US because of his long record of IRA activity, including a three-year sentence for attempting to smuggle arms from Libya in the 1970s. In 1942 he was sentenced to death for killing a policeman in the Lower Falls Road in Belfast but his sentence was commuted.
After the split in the IRA in 1969 he was one of the leaders of the Provisional wing and its first commander in Belfast.
By granting Mr Cahill a visa in the face of British objections the Clinton administration has shown again that it has distinct views on Northern Ireland - unlike President Bush and President Reagan who almost entirely endorsed British policy. Because of Mr Cahill's well-known former membership of the IRA the visa could not be authorised in Dublin but had to be granted in the US.
President Clinton had to personally clear Mr Cahill's visa, and it will now be difficult for the State Department to deny entry to any Provisional supporters wishing to follow him.
Another sign of the Administration's interest in Ireland is its willingness to offer up to dollars 200m ( pounds 133m) in reconstruction aid to Northern Ireland if there is a permanent peace agreement. Although the aid has not been finalised, it is patterned after a package given to South Africa after the election of Nelson Mandela as president earlier this year.
The Irish lobby in Washington has been much more effective under President Clinton than it has been for many years. This is partly a tribute to the influence of Senator Edward Kennedy, whose office was largely responsible for getting the earlier visa for Gerry Adams in the face of opposition from the State Department and the British government.
It is unclear if Mr Cahill's visit will enjoy the same publicity as Mr Adams's tour of the main television talk shows. But as a founder of Noraid, the main organisation of Provisional sympathisers in the US, his arguments in favour of a ceasefire are likely to carry weight.Reuse content