it was a scare tactic.....Tom knew that Luca was a feared man, and that he was loyal to Vito.....that was Vito's downfall, he asked Luca to go to the Tatallias and act unhappy.....they all knew it was a set up...so they were ready for Luca before he even got there.
So Tom was trying to get Solozzo to back off......that's all.