(CNN) Special counsel Robert Mueller continues to press for an interview with the Russian oligarch and his pop star son who encouraged Donald Trump Jr. to meet in June 2016 with a Russian lawyer promising dirt on Hillary Clinton.

The conversations between the attorney for Aras Agalarov and his son, Emin, and the special counsel have been ongoing for nearly a year, Agalarov's attorney said Thursday. The continuing back-and-forth is a sign of the lasting special counsel interest in investigating the circumstances of the controversial campaign-year discussion.

"We've been having conversations with the special counsel for a potential interview for nearly a year. Those conversations are not new. They are ongoing. We haven't reached an agreement yet on any terms of such an interview and I can't predict whether we will reach agreement or not," said Scott Balber, the attorney for the Agalarovs.

Mueller's team is interested in discussing the Trump Tower meeting and the talks around the building of a Trump Tower in Moscow, according to Balber. The tower was never built.

Balber added that his clients have no reason to believe Trump knew about the meeting with the Russian lawyer before it happened. Last week, sources told CNN that former Trump lawyer Michael Cohen claims to have information about Trump being informed about the meeting and its purpose before it happened.

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