IT WAS all over in a few minutes. But Attorney-General Janet Reno's White House 'press conference' on Thursday amounted to the biggest reversal in Washington's policy towards Cuba in almost three decades. The professed reason was 'to deter more Cubans from risking their lives'. But the message was stunning. No longer will the US automatically accept every Cuban refugee. The last thing President Clinton needs is a repeat of the Mariel boatlift 14 years ago, the previous occasion when a beleaguered Fidel Castro opened the emigration sluicegate.

For Mr Clinton, Mariel is a painful memory. Many of the 125,000 refugees were sent to Fort Chaffee, Arkansas. One Sunday, hundreds rioted, spilling into the countryside. Arkansans were outraged, blaming a first-term governor called Bill Clinton for caving in to Washington and accepting the refugees. The 'Cuban mess' helped sweep Mr Clinton from office in that November's election. For a president who nurses hopes of carrying Florida in 1996, need any more be said?

The state's present Democratic Governor, Lawton Chiles, is up for re-election in two months. The 8,000 or so Cubans who have arrived so far in 1994 may be only a trickle compared to the Mariel flood but for the Governor's uncertain re-election prospects, they could be the trickle which breaks the dam. Like the Haitian one before it, argues Mr Chiles, the Cuban influx is at least as much the responsibility of Washington as of Florida. Even so, his entreaties on Thursday initially fell on deaf ears at the White House. Then came Ms Reno's reversal.

One reason may be reports suggesting tens of thousands more Cubans were about to attempt the crossing of the Straits of Florida. But for whatever proximate reason, Washington has made the first major change in immigration policy since the 1966 act which effectively granted automatic asylum to Cubans who reached the US or were picked up at sea.

With this week's shift, the US is moving to correct two inconsistencies. One is the gap between its words and deeds on emigration from Cuba. Proclaimed policy is to encourage 'safe and legal' migration. In fact, legal visa applications to the US Interests Section in Havana have been granted at 5,000 a year, compared to the 20,000 permitted by a 1984 Cuba-US deal aimed at preventing another Mariel. But let a Cuban to the shark-infested waters on a raft, and he is certain of asylum.

The other is the different treatment accorded Cuban and Haitian refugees. Despite fleeing equally oppressive conditions, the latter face repatriation or internment at Guantanamo Bay or some other prison-like transit centre. In Haiti's case the formula has slowed the exodus. Mr Clinton hopes the Cuban measures, albeit avoiding forced repatriation, will do the same, while not upsetting Florida's influential Cuban- American community.

In the longer term, the measures could inrease pressure for more direct intervention in Cuba. 'If Clinton now treats Cuban refugees like Haitian refugees,' said Julio Estorino, host of a Spanish- language Miami radio station, 'then he must treat Castro like he treats (Haitian strongman Raoul) Cedras' - in other words, be prepared to invade. That Mr Clinton would never do. Washington still hopes the Castro regime will collapse of its own accord. But many Cuba specialists say stiffer immigration procedures ought to be only a start. Why not lift the comprehensive US embargo? This would deprive Mr Castro of his argument - that Cuba's plight is the result of Yanqui economic warfare - and possibly hasten his downfall.

(Photograph omitted)