'Hamilton contract delay has to be about money'

Asked for an opinion during a Monaco Grand Prix news conference on Thursday, Horner was sure the delay was all down to cash and what his Mercedes counterpart Toto Wolff was prepared to pay.

"I should think it's such a grotesque amount of money that Toto is talking about, it probably is what's making his and Niki's eyes water at the moment," he said, also referring to Niki Lauda, the Mercedes F1 non-executive chairman.

"He (Hamilton) has an expensive lifestyle. He's a four-time world champion and I doubt he's cheap. I can only envisage that that's probably got something to do with the delay."

Talks between Mercedes and Hamilton, who is out of contract at the end of the year, have been going on since 2017 and have turned into something of a saga.

Hopes of a deal by the end of last year turned into the possibility of something being sorted before the season opener in Australia in March and have since been pushed back from race to race.

Both parties say they intend to renew and that there is no urgency.

Wolff, who was in the same news conference as Horner, said both had confidence in the other and saw no reason why it should not happen.

"There is a bit of email ping-pong on details," the Austrian added.

"I don't want to set a date because then you will be asking me why, why hasn't it been done, but maybe we choose one of the nice Grands Prix in the future, in the next couple of months."

Hamilton is leading Ferrari's Sebastian Vettel by 17 points in the championship after five races, having won the past two in Azerbaijan and Spain.