British media have reported that Premier League clubs will soon meet to discuss the idea of shutting the window earlier in a bid to avoid players being unsettled by interest from rivals.
Bilic said that teams were often forced to completely rejig their starting line-ups when transfers robbed them of key players after the season started.
"Some teams lose 30% of their team, but it definitely should be across Europe otherwise there is no point," the manager told a news conference.
Bilic said he understood the plight of managers fighting to hold on to their prized assets. The Croat had to deal with the same situation at the start of the year when one of his top players, Dimitri Payet, refused to play for the club in order to force a move to Olympique de Marseille.
"Of course, I have sympathy... You want to have your team and concentrate only on the game and you're not because of those things," he added.
While media reports have suggested Liverpool could look to West Ham's Manuel Lanzini if they lose midfielder Philippe Coutinho to Barcelona, Bilic said the Argentine was settled in west London and focused only on Saturday's Premier League game at Southampton.
"He really feels at home here," Bilic added. "He feels wanted. He knows if he has a good season at West Ham, he has the chance to improve... and to play for Argentina."