The 43-year-old indicated that it is "normal" for negotiations to take time, bemoaning the influence of agents, while stressing the player "loves" the club and will not walk away
The Austrian has 17 months remaining on his current deal and recent speculation has suggested the conversations have hit a wall.
But the former Norwich manager played down the validity of the rumours, assuring fans that everything is normal and pointing out there are more important things to be worrying about with the Midlands club stuck in a relegation battle.
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"Have contract talks stalled? No, we are still talking. I've spoken to him and everything is fine. Talks are ongoing but that's normal when you are trying to negotiate.
"Andi loves it here. I've spoken to him. I think there are more important things at this moment in time than worrying about contracts.
"He's still under contract so at the minute it's fine. I don't think he'll walk away. I don't. I think everyone knows agents can inflate people's salaries."
The 21-year-old, who has played for his country from Under-17s upwards, moved to Villa Park from Rapid Vienna as a youth player in 2007 and has netted 10 goals across all competitions this season.
The attacker faces a tough test if he is to add to that tally in the club's next league match on Monday night, though, with Lambert's men playing host to second-placed Manchester City.