Cahill will be a key figure for the Australian national team at the tournament, which kicks off in Qatar on January 7 and runs through to the 29th, but Moyes says that the Merseyside club should not be responsible for paying the 30-year old during that time.
"They are due to take Tim in mid to late December (for a training camp) and depending how far they go in the tournament will determine how long he is away," Moyes told the Liverpool Echo.
"I'm trying to delay him going until January and will do the best I can but I think it's unfair.
"I just feel in this world where the money is so tight for clubs, someone might say if you want to play in that tournament then there will be no wages in that month.
"We can't stop you playing for your country, but maybe there are no wages.
"You cannot turn round and say 'bring yourself in line with us' because their weather or their seasons are different from us.
"You can't ask them to change, but maybe if you are going to take the player away in the middle of the season should a club get reimbursed?
"If that was the case I don't think it would happen because those countries can't afford to.
"If 10 Australian players were playing in Europe then surely they couldn't afford to pay their wages each for a month.
"If you were an owner of a club you would be disappointed about paying the wages of these players and not getting the benefit of them at that time."