New Zealand Group One plans will go on the line for two of the favourites in an Expressway Stakes meeting support race at Randwick on Saturday.

Rule Book and Celtic Price are vying for favouritism in the Liberty International Underwriters Handicap - a 2400m event that will have a bearing on Auckland Cup ambitions for the pair.

Emerging trainer Bjorn Baker confirmed the in-form Celtic Prince is in contention for a $NZ500,000 ($A465,000) Auckland Cup start as he chases his fifth victory in easily his most profitable campaign.

Celtic Prince outstayed Rule Book in a Warwick Farm win on January 11 to put the Auckland Cup on Baker's list of possible feature-race options for the much-improved stayer.

"It would be something to go back home with a horse that's done all his racing here and win the Auckland Cup," Baker told NZ Racing.

Baker trained Unemcumbered to win the $2 million Magic Millions Classic last month but is still searching for his first Group One win.

Rule Book ($3.20) is one of four stayers trainer Gai Waterhouse has entered for the Ellerslie feature on March 5.

The five-year-old, who is shading Celtic Prince ($3.40) at the top of the market, won three races in England before finding his way to Australia.