The Italian team was not immediately available to respond to reports published by German media late Monday, which said talks between Vettel and the Italian racing powerhouse had broken down.
Germany’s best-selling tabloid Bild and Auto Motor und Sport both reported the 32-year-old, who will be out of contract at the end of 2020, had rejected the terms offered in a new deal.
The newspapers said the separation with Ferrari, the sport’s oldest and most successful team, could be announced officially on Tuesday.
Ricciardo, at Renault, and McLaren’s Spaniard Carlos Sainz have both been mentioned in media reports as leading candidates to take one of the most coveted seats on the grid.
Both are also out of contract at the end of 2020.
Six-times world champion Lewis Hamilton has also been linked to Ferrari but has repeatedly indicated he intends to stay with Mercedes.
Italy’s Gazetta dello Sport newspaper recently reported Vettel was being offered a one-year extension with a salary reduction.
Vettel joined Ferrari in 2015 after winning all of his titles with Red Bull and dreaming of emulating his boyhood hero Michael Schumacher, who took five of his seven titles with the Maranello-based team.
The father-of-three told reporters last month he could have a new deal done before the start of a season delayed by the COVID-19 pandemic.
Ferrari have said the German was their first choice to partner Charles Leclerc but reports in Italy said they wanted an answer by the end of April to ensure potential replacements were still available.
Leclerc, who won two races last year and is only 22, has a contract until 2024 and is seen as Ferrari’s future and likely first champion since Kimi Raikkonen in 2007.
The Monegasque outperformed Vettel in his first season at Ferrari last year, finishing ahead of him overall and taking more points, poles, podiums and wins.
Formula One has deferred to 2022 a major technical rule change planned for 2021, meaning teams will use the same cars next year as this.
Ferrari appeared to be behind Mercedes on pace in pre-season testing but have not been able to run their car in race conditions due to the March 15 Australian opener being cancelled.
The sport hopes to get going behind closed doors in Austria in July.
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