BRACING for an international invasion of unprecedented size, Racing Victoria’s Greg Carpenter concedes locally-trained horses face a difficult challenge to keep the Melbourne and Caulfield Cups in Australia.

With Humidor heading the weights for both Cups with 58kg, Carpenter expects northern hemisphere runners to target the spring carnival in record numbers. There are 50 raiders among the 183 Melbourne Cup entries and 27 among the 164 Caulfield Cup entries.

“At this point, it looks as though we can expect a record number of international runners across the spring racing carnival, so locally-trained horses could face a tough task in ensuring the cups remain here in Australia,” Carpenter said.

“That said, with horses like Kings Will Dream, Unforgotten and Ace High prominent in the early betting markets, I’m sure the overseas raiders won’t have it all their own way.”

Overseas runners filled nine of the first 11 places in last year’s Melbourne Cup when Rekindling led home Johannes Vermeer.

Both Rekindling and Johannes Vermeer will not contest the Cups this season.

Carpenter said it had been challenging constructing this year’s Melbourne Cup weights, but rates Humidor, who chases a fourth Group 1 in Saturday’s Makybe Diva Stakes, as a worthy topweight.

“There’s no doubt in my mind he is the best-performed and highest rated horse in both races,” Carpenter said. “It’s been a challenging year this year in constructing the weights because there is no natural topweight in both races this year.”

Since Makybe Diva retired in 2005 after posting her third Melbourne Cup win, only Fiorente (2013) has failed to defend his crown.

International raiders Best Solution (Godolphin) has 57.5kg in both Cups.

Aidan O’Brien’s trio – Lancaster Bomber (57.5kg), Cliffs Of Moher (56.5kg) and Idaho (56kg) – are prominent in the weights.

Torcedor, now trained by Andreas Wohler, has 57kg.

RV is confident up to six internationals will feature in the Caulfield Cup, led by Chestnut Coat, Folkswood, Emotionless, Red Verdon, Teodoro and Sole Impact.

Weir-trained Kings Will Dream, the TAB’s ruling favourite for both races, will carry 53kg.

Last year’s Victoria Derby winner Ace High is the highest weighted four-year-old in the Cups with 55kg.

The O’Brien-trained Kew Gardens, who is the favourite for Saturday’s St Leger at Doncaster, has 53kg for the Melbourne Cup.

Aidan’s son Joseph O’Brien, who trained Rekindling, will pin his hopes this year on Irish Derby winner Latrobe who has 52kg.

“With incredibly talented horses like Best Solution and Torcedor coming from Europe, the return of Japanese contenders led by Chestnut Coat, proven Australasian Group 1 performers like Humidor and an outstanding crop of four-year-olds, we will crown a worthy champion in the Caulfield and Melbourne Cups,” Carpenter said.