Toto Wolff plays down meeting with Jos Verstappen in F1 paddock at Monza

After a recent run of reliability problems, Max Verstappen's long-term future at Red Bull has been thrown into doubt.

Verstappen is currently committed to Red Bull for 2018 but there are understood to be some options that could allow him to leave as early as 2019.

A chat between his father Jos and Wolff at Mercedes on Friday at Monza fuelled speculation about Verstappen's future, but the Mercedes boss insists the meeting was just a social one.

"I've known Jos for many years," Wolff told Sky Germany about the meeting. "We have a common friend, Frank. He is on a visit here.

"So Niki [Lauda] and I sat in the office. Our Dutch friends came along and we had a coffee with them. Not more, not less."

Asked whether there was any interest in Verstappen as a Mercedes driver in the future, Wolff said: "For next year no interest in Max Verstappen. He is not available."

However, Wolff said that Mercedes was keeping an eye on a host of youngsters for 2019 onwards.

"He is one of the names you have to have on the radar," he said. "Max is one of the future stars of Formula 1.

"Like many others, like Valtteri [Bottas], like Daniel [Ricciardo]. Max and Esteban Ocon are part of this group of drivers as well."

Mercedes will keep Valtteri Bottas for 2018 after a strong first campaign for the team, but there remain questions about how long his contract extension will be.

Wolff added: "It's all about the details. It's a no-brainer to continue with Valtteri.

"He has done a really good job this year. He's had his lows as well, which he needs to understand. But we couldn't expect more from his first year."