AMERICAN husband and wife team David and Karen O'Connor, both making their Olympic debuts, swept the home side into the lead after the first day of dressage in the team three-day event yesterday. Both were riding Irish exports and with a 3.8 point advantage over the British, America will be hoping to reproduce the form that took its team to Olympic gold the last time the Games were held on US soil, in Los Angeles, 12 years ago.

Ireland, represented in the dressage by David Foster and Virginia McGrath, are placed ninth.

Scottish rider Ian Stark, whose personal tally of Olympic medals numbers three silvers, took the early lead with a superbly stylish test from the grey thoroughbred Stanwick Ghost. His mark of 35.2 remained in front throughout the day, but individual scores no longer count following the IOC decision to split the team and individual competitions after the Games in Barcelona.

Stark's score was backed up by a mark of 49.0 from British number two William Fox-Pitt, whose test was marred by Cosmopolitan's break in the second counter-canter movement, to give the British a total of 84.2.

But the American couple were riding at the top of their form and, after a supremely confident test from Karen O'Connor and the giant Biko for a mark of 39.6, the hosts were then catapulted into the lead when David O'Connor, second-last into the arena yesterday afternoon, posted a score of 40.8 with Giltedge, the gelding formerly campaigned on the Irish circuit by Eric Smiley.

Karen O'Connor rode Biko to third place at Badminton last year and that feat was mirrored by her husband, David at the Gloucestershire event this spring with yet another Irish-bred the 10-year-old Custom Made which O'Connor will be riding in the individual competition later this week.

Two other Olympic debutantes put the Canadians into overnight third. A mark of 40.0 for Therese Washtock and Aristotle gave the Canadians a good start and this was then backed up by Kelli McMullen-Temple, whose test with the eight-year-old Irish thoroughbred Kilkenny seemed harshly marked at 47.2. It was good enough to put the Canadians well in reach, on 87.2. just three points behind the British.

David Foster, a veteran of both the Los Angeles and Seoul Olympics. was called upon to act as pathfinder for the Irish and more than justified the faith of chef d'equipe Helen Cantillon-O'Keeffe. Well aware that dressage is not the strongest point in Duneight Carnival's armoury, Foster coaxed a lifetime's best from the 12-year-old chestnut for a mark of 52.2 that kept the Irish well in contention during the morning session.

Foster had ridden the gelding for just 20 minutes before his test which was in stark contrast to the amount of work put into The Yellow Earl by Irish number two Virginia McGrath, who still had her hands full with the 10-year-old thoroughbred, even after 1 1/2 hours work in the worst of the heat.

The Yellow Earl was ready to explode at any moment during the eight-minute test, but McGrath maintained a cool head throughout and managed to contain the chestnut's volatile temperament to score 61.8, leaving the Irish ninth of the 16 teams.

But the Irish chef d'equipe remains confident that her squad can get closer to the medals during tomorrow's cross-country.

"They'll just have to kick on," she said, after yesterday's dressage.

The Irish quartet has plenty to attack on Roger Haller's 25-fence cross-country track, which covers just over 3 1/2 half miles of undulating terrain that is sure to sap stamina already sternly tested by the combination of high heat and humidity.

Rumours that concern over threats from the animal rights lobby to have the competition stopped would cause Haller to reduce the severity of his cross-challenge have proved unfounded. Many of the riders have been surprised that the course still asks so many uncompromising questions.

Mark Phillips, former son-in-law of the Queen and an Olympic equestrian gold medallist, has barely raised a British eyebrow by coaching the American team in Atlanta. Joining the breakaway colonies might have caused a scandal in the days of King George III but Phillips has survived the switch without rancour.