Southampton will report Liverpool to the Premier League over an alleged illegal approach for centre-back Virgil van Dijk, reports BBC Radio Solent.
The 25-year-old wants to move to Anfield if he leaves St Mary's.
The £50m-rated Netherlands defender signed a new six-year contract last year, having joined Southampton from Celtic for £13m in September 2015.
Liverpool are yet to formally approach Saints to ask for permission to speak to Van Dijk.
The Reds refused to comment on renewed speculation on Monday, while Southampton are adamant they do not need to sell the defender.
Saints are irritated by what they see as an attempt to unsettle Van Dijk and are ready to reject an official offer.
Chelsea and Manchester City have both been heavily linked with the Dutchman, but City's interest has cooled as they are not prepared to pay as high a fee as Liverpool.
Former club Celtic are also understood to have a 10% sell-on agreement.
Van Dijk missed the final five months of the season after sustaining an ankle injury following a challenge by Leicester City's Jamie Vardy in Southampton's 3-0 win at St Mary's on 22 January.
It forced him to miss Southampton's EFL Cup final loss to Manchester United at Wembley.