The 31-year-old, who is the Balkan country's all-time leading scorer with 48 goals, quit Bulgaria in 2010 and has repeated several times since then that he had no intention of changing his mind.
"You should receive an invitation to return somewhere," Berbatov told Bulgarian sports website www.sportal.bg.
"My phone is switched on and I can be more concrete if I receive an invitation.
"No one has tried to contact me. I haven't met [Bulgaria coach] Lubo Penev and I haven't talked to him. I couldn't even congratulate him on his appointment."
Penev, who replaced German Lothar Matthaus in November, was planning to meet Berbatov this week.
"I'll talk to him this week and I'm optimistic," the coach, whose first match in charge is a friendly against Hungary on February 29, told Bulgarian state television.
"I think this is the right time for such a meeting."
Berbatov, joint top scorer in the Premier League last season, has lost his starting spot at United and Bulgarian pundits have suggested the striker could have a change of heart over the national team in an attempt to revive his club career.
Bulgaria captain Stilian Petrov broke his four-and-a-half media silence in October to urge Berbatov to consider returning to the national team because they need their "most talented player."
The team have been drawn in a tough World Cup qualifying group and will face Italy, Denmark, Czech Republic, Armenia and Malta as they bid to reach the 2014 finals in Brazil.
