The deadline has arrived for European horses targeting the $2.5 million Caulfield Cup next month with the requirement that they enter quarantine at Newmarket in England.

Caulfield Cup first acceptors likely to commence quarantine are American St Leger winner Dandino, Ascot Gold Cup runner-up Simenon, Glorious Stakes winner Forgotten Voice and the French-trained, Australian-owned Trevieres.

However, international stars Red Cadeaux and Royal Diamond have been ruled out and will instead be aimed at the Group One Irish St Leger (2800m) at The Curragh on Sunday.

"The connections of Red Cadeaux and Royal Diamond were both interested in contesting the Irish St Leger and the BMW Caulfield Cup, but unfortunately our quarantine requirements would not allow it," said RV international recruitment officer Leigh Jordon.

He said that while the two horses would miss the Caulfield feature he remained hopeful they would contest the Melbourne Cup.

"Red Cadeaux was beaten by the narrowest margin in Melbourne Cup history two years ago and I know that his connections, in particular, are very keen to atone for that if the horse is fit and well," Jordan said.

The quarantine deadline for Europe's Melbourne Cup aspirants is September 26.

Weights for Australia's most famous race will be released on Tuesday.