Wanderers are expecting to hear on Tuesday whether Israeli international Tal Ben Haim has been successful in his application for a work permit.
Once the formalities have been completed, the 22-year-old will sign a three-year contract.
"That is our only concern now," Allardyce said. "Everything else is more or less agreed.
"He's apparently one international short of the required 15 but we shouldn't have any problems."
Ben Haim is keen to join Wanderers after getting to know the players and management on the Portugal tour.
He struck up a good relationship with Jay-Jay Okocha and said: "I had a good chemistry with the players and the staff.
"There are a few things to be resolved but they are not big ones.
"I am happy but I will be happier when I sign the contract."
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