Sevilla defender Diego Carlos has told the club he wants to leave this month to join Newcastle.
The Brazilian is writing a transfer request to send to the club's manager and president after Newcastle had submitted a bid for him earlier this month.
Sevilla are willing to do business with Newcastle at the right price, but the Magpies will not pay over the odds for the 28-year-old and have other centre-back targets.
Newcastle are hoping to sign two central defenders this January.
The Premier League club retain a strong interest in Benoit Badiashile, but a deal for the Monaco defender is now looking unlikely after he sustained an injury during his side's draw with Nantes.
Another stumbling block is Monaco's asking price, with the Ligue 1 side looking for a fee in the region of €60m (£50m) for the 20-year-old.
Newcastle are also interested in Fenerbahce's Hungary defender Attila Szalai.
Sky Sports News has been told the 23-year-old, who played in every minute of his country's Euro 2020 campaign, is also attracting attention from AC Milan.
It is thought Szalai would cost in the region of £16.7m (€20m). His contract at Fenerbahce runs until 2025.
Lille's Sven Botman was their primary centre-back target, but the French club are only willing to do business for around £36m.
Carlos, who won a gold medal at the Tokyo Olympics with Brazil in the summer, has made 28 appearances for Sevilla this season, scoring two goals.
Eddie Howe's desire to improve his defence is understandable, with his Newcastle side having conceded 43 goals in just 20 Premier League games this season. Only Norwich have a worse defensive record.
'Carlos doing everything possible to make Toon deal happen'
Sky Sports News' Kaveh Solhekol:
"Diego Carlos is thinking that if I'm the one Newcastle want to sign and I know they really want me, then I'm going to have to do everything possible to make this deal happen so I need to tell Sevilla officially that I want to leave.
"It's been reported in Spain that Carlos may have a release clause of around €80m.
"Newcastle are arguably the richest club in the world, but they won't want to pay over the odds and have other targets.
"I don't think Carlos would move just for the money. Of course the financial package on offer has to be right. He knows Newcastle are building something and they have the finances to build something as well."
Sky in Italy: Newcastle fail in Zapata bid
Sky Sports News' Kaveh Solhekol:
"Our colleagues at Sky in Italy are also reporting Newcastle have tried to sign Duvan Zapata, the Atalanta striker.
"They're saying Newcastle's offer was €5m for a loan, with an option to buy for €26m.
"Sky Italia are saying the operation was 'impossible' with these figures, and Atalanta will only change their minds should Newcastle come back with an increased offer."
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