Undaunted by his lack of success in the Kentucky Derby, Europe's leading trainer Aidan O'Brien is eyeing a raid on some of American's top second-half season races – with the Travers Stakes at Saratoga on August 23 high on the agenda. O'Brien was frustrated in his plans to run Hold That Tiger in Kentucky, chiefly because of the quarantine regulations which prevented him from stabling a runner at Churchill Downs. His team has been slower than usual to come to hand this season, a likely consequence of last year's virus, meaning that the Belmont Stakes will probably come to soon for the 3-year-old colts he trains with U.S.-orientated pedigrees. But O'Brien sad: "We are looking at running some of our 3-year-olds on the dirt. We are thinking about the Belmont although that may come too soon. So the Travers is more likely. "Hopefully if we have the horses we'd have plenty of time to go on with them in the second half of the season. We haven't really got the horses properly sorted yet." Likely American runners would include: -- Statue Of Liberty (a $1.3 million son of Storm Cat out of Charming Lassie, by Seattle Slew), who has not run since winning last season's Coventry Stakes at Royal Ascot but is due to reappear in the Irish Two Thousand Guineas at the Curragh on May 23. -- Tomahawk (a $2.5 million son of Seattle Slew out of the Statuette, by Pancho Villa) who had little luck in running behind subsequent French Two Thousand Guineas winner Clodovil in a Longchamp trial before finishing eighth in the Two Thousand Guineas at Newmarket -- Van Nistelrooy (a $6.4 million son of Storm Cat out of Halory, by Halo), a highly rated two-year-old who has not been seen out so far this season. O'Brien remains keen to target the Kentucky Derby despite the quarantine problems and disappointing show last year from Johannesburg."We definitely want to have runners again, although the quarantine regulations are a bit messy for us," O'Brien said. "I think in time they will change it, because everything changes. It would be very good for the race itself to make the quarantine regulations more friendly for everyone. We can't force that to happen but in time it will happen. That would bring the percentages a little closer to us because at the moment it's miles away. For racing in general I think it's important that the European and the American horses can compete together, to bring the world together for all the people who are breeding horses."