Ricciardo using Hamilton to 'blackmail' Red Bull

Mercedes chief Niki Lauda says Daniel Ricciardo is "blackmailing" Red Bull in contract talks, after their motorsport advisor Dr Helmut Marko confirmed that his driver will not decide his future with the team until Lewis Hamilton finally commits to the world champions.

Ricciardo was expected to play the key role in the 2019 driver market in his final year of contract at Red Bull, however Hamilton's continued refusal to extend his own deal has muddied the waters.

Four-time world champion Hamilton is also out of contract at the end of the year, and had been expected to sign on in pre-season. However, a new deal remains unsigned six races into 2018.

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Marko and Lauda were in conversation at an event at the Red Bull Ring, as reported by Kronen Zeitung, where MotoGP champion Marc Marquez was testing a Formula 1 car for the first time.

Lauda once again stated that a new deal for Hamilton is only a matter of time, claiming "little things" were only left to be finalised.

However, it appears that the reigning champion's hesitance is having an impact across the grid.

"Ricciardo doesn't want to sign until Hamilton has signed," Marko said.

"It's a bit strange. Hopefully it ends soon."

Lauda clapped back, claiming not to have even considered signing the Australian, who he accused of holding Red Bull to ransom.

He said: "Ricciardo blackmails you with Hamilton, who has not yet signed?

"We have not made him an offer, so he can wait forever."

Marko also suggested that someone within the Silver Arrows camp did not want to sign Ricciardo, reportedly referring to Toto Wolff, although Lauda insisted he is "the supreme" in terms of having the final say on signing drivers.