Damien Oliver's chances of landing a fourth Melbourne Cup have been enhanced as he now has the option of riding either of Danny O'Brien's key chances.

Speaking on RSN radio, O'Brien said Oliver would have the option of choosing between Russian Camelot and defending champion Vow And Declare for the Melbourne Cup.

Last year Craig Williams rode Vow And Declare to his Cup victory but this spring he has committed to Surprise Baby.

Williams had said he would make a decision as to whether he would ride Surprise Baby or Vow And Declare in the Cup later in the spring but O'Brien ended that speculation.

O'Brien has four horses being aimed at the Melbourne Cup which are Vow And Declare, Russian Camelot, Orderofthegarter and King Of Leogrance.

Russian Camelot will run in the Underwood Stakes at Caulfield on Saturday and the trainer is confident he will perform well.

"His gallop at Flemington on Tuesday was very good," O'Brien said.

He said Russian Camelot's first target for the spring was the Cox Plate and then they would make a decision on a Melbourne Cup start.

Russian Camelot has only had six starts and he resumed with an unlucky second in the Makybe Diva Stakes behind Fierce Impact.

"He's still a lightly-raced horse and I expect him to improve every time he goes to the races," O'Brien said.

O'Brien believes Vow And Declare is going as well as last year and he will run in the Turnbull Stakes at Flemington on Saturday week, a race he finished fourth in 12 months ago.

O'Brien is also pleased with King Of Leogrance who will run in the Turnbull Stakes and then have one other start before the Melbourne Cup.

The trainer has decided that last Saturday's Naturalism Stakes winner Orderofthegarter will contest the Herbert Power Stakes at Caulfield, a week before the Caulfield Cup.