The classy stayer has won the Cesarewitch and the Northumberland Plate on his last two outings, two of the richest handicaps of their type in Europe, and is favourite with some firms for the Flemington showpiece.
However, the Tony Bloom-owned five-year-old is still way down the list of acceptors, in a race in which only 24 can go to post.
“No decision has been made what to do yet. He is in quarantine and is due to fly to Australia next Thursday, I believe,” said Charlton.
“I think it’s going to be tough to get into the Melbourne Cup. Some above us might not run and some might not travel, so things can change.
“We’ve been encouraged all the way along that we would get into the race, but it has been so popular it has made it a tough race to get into.
“It would be disappointing if we didn’t get into the race having been encouraged all along.
“The only way of getting more weight is by winning another race out there. On the prize-money front, he is top of his bracket.
“One of the races will be too tight with quarantine, but there is the Geelong Cup. However, I’m not sure about that and that is not necessarily the plan.”