The 27-year-old has refused to talk about a contract extension with his current side and favours a move to the Birmingham club, says sporting director Martin van Geel
The 27-year-old has met with Villa and favours a move to the Premier League after turning down the chance to extend his contract with the Eredivisie side.
Van Geel also stated that the centre-back has a buy-out clause in his contract, but refused to reveal the price - though he did state that it would not be a cheap option for Paul Lambert's men, though according to Algemeen Dagblad, Villa are prepared to meet the cost.
The Dutch club took two official squad photos on Monday, one with Vlaar in the team, and one without - meaning that they are prepared for a departure in the near future.
"Ron visited Birmingham yesterday and wants to continue his career at Aston Villa," Van Geel stated to RTV Rijnmond.
"We met with him last week to discuss a contract extension, but that was not an option. It's true that he has a buy-out clause. I won't reveal how much exactly we're talking about, but we're obviously talking about millions here."
If Villa do secure the services of Vlaar, it will be new manager Paul Lambert's third summer signing, after capturing ex-Sheffield United defender Matthew Lowton and Vlaar's former team-mate Karim El Ahmadi - though there has been another arrival with former boss Alex McLeish's signing of Australian midfielder Brett Holman.