The international dominance of this year's $6.2 million Melbourne Cup, led by joint topweights Dunaden and Americain, has been emphasised by the handicaps for the race.

Defending champion Dunaden and the 2010 winner Americain, were both handed 58kg for this year's Cup, meaning they will have to prove the equal of the great Makybe Diva to win again.

Of the top 20 horses in the weights released on Tuesday, 17 are either internationals or imports, and two of the three locals, More Joyous and Southern Speed, are unlikely to run.

In the past 40 years only two horses have won the Cup with 58kg or more, the most recent of them Makybe Diva who carried that weight to her third straight victory in 2005.

Dunaden and Americain have one kilogram more than the former English-trained Manighar, although Peter Moody's gelding is likely end his spring campaign in the Cox Plate.

The only other previous winner entered is nine-year-old Efficient who won the 2007 Cup with 54.5kg and has 55kg this time.

One of the joint favourites, the English entry Mount Athos, has 54kg and the other, Green Moon, an Irish import, has 53.5kg.

Racing Victoria handicapper Greg Carpenter said Dunaden and Americain would have to step up if they were to repeat their successes.

"It should always be a challenge to win the Melbourne Cup and more so to win it twice," Carpenter said.

Of the 55 horses who have returned for successive Cups, only five have been multiple winners, and only four of those in the following year.

"Dunaden last year followed the blueprint of Americain, winning the Geelong Cup and then the Melbourne Cup with 54.5kg and like Americain last year I've progressed him 3.5kg in the weights to 58," Carpenter said.

Red Cadeaux, runner-up last year in the closest ever Cup finish, is seventh in the weights, carrying 55.5kg.

"Last year Dunaden had a kilo more than Red Cadeaux and it was that breathtakingly-close finish so this year there's 2.5kg difference," Carpenter said.

"They went to Hong Kong and ran at level weights and Dunaden won and Red Cadeaux was placed.

"They also matched up in the Hardwicke Stakes this year in the Royal Ascot carnival and again Dunaden proved to be Red Cadeaux's master.

Only three horses who have run second in the Melbourne Cup have returned the following year and won - Empire Rose, Gold and Black and Carbine.