Daniel Ricciardo has put his Red Bull talks on hold until Lewis Hamilton signs a new deal at Mercedes, according to Dr Helmut Marko.

Red Bull wants Australian Ricciardo to stay, but he is being linked with Ferrari and Mercedes.

However, team chairman Niki Lauda says that Hamilton is definitely staying at Mercedes.

"Lewis is staying with us," he is quoted as saying by Kronen Zeitung at an event at the Red Bull Ring. "[The contract delay] is only about little things like promotion."

Yet Marko says that Ricciardo has told Red Bull that he is waiting for Hamilton.

"Ricciardo doesn't want to sign until Hamilton has signed," he said. "It's a bit strange. Hopefully it ends soon."

Lauda, a shrewd contract negotiator, said that he thinks Ricciardo's tactic is akin to "blackmail".

"We have not made [Ricciardo] an offer," Lauda insisted. "So he can wait forever."

The good news for Red Bull is the form of both the 2018 car and Ricciardo, who is not ruling out a championship tilt.

Ricciardo could take some 'power unit' component change penalties this weekend in Canada, but Marko said that the team will at least get a minor horsepower boost.

"We're getting a Renault upgrade for Canada," he said.

After that, Red Bull needs to decide whether it will stay with Renault for 2019, or switch to Honda.

"We have an internal timetable that we want to have decisions on the engine and driver issues by the Austrian Grand Prix," Marko said.

Red Bull currently trail third-placed Ferrari by 49 points in the constructors' standings.