Trainer Joseph O'Brien believes Iridessa has shown she will stand up to the stamina test in the Irish Oaks at the Curragh.

Iridessa finished fourth over a mile in the Irish 1000 Guineas in May and appeared to improve for a step up to 10 furlongs (2000m) when an impressive winner of the Pretty Polly Stakes three weeks ago.

She takes another step into the unknown over a mile and a half (2400m) on Saturday (Sunday AEST) as she bids to give her trainer a second Classic success, following the Irish Derby triumph of Latrobe last summer.

"Iridessa has come out of the Pretty Polly Stakes well and she didn't look like she was stopping that day, so we are looking forward to it," O'Brien said.

"We were over the moon with her in the Pretty Polly, and she really thrived on the step up in distance that day. We think going further this weekend will probably be fine for her as well, but it is always a bit of an unknown - how they will get the extra two furlongs."

His father Aidan O'Brien has already saddled five winners of the Irish Oaks, and holds a strong hand in search of his sixth.

Pink Dogwood has arguably the best mile-and-a-half form having been beaten a neck in the Oaks at Epsom, but was 3-1/2 lengths behind Iridessa in the Pretty Polly.

Aidan O'Brien also saddles Epsom third Fleeting - who has since finished second in the Ribblesdale Stakes at Royal Ascot - and recent course winner Peach Tree, who seems likely to be deployed as a pacemaker.

The British challenge is headed by the John Gosden-trained Star Catcher.

Gosden has won the race with Great Heavens (2012) and the brilliant Enable (2017), while jockey Frankie Dettori has four Irish Oaks wins on his CV.