Lewis Hamilton
Kimi Raikkonen (right) won the 2018 U.S. Grand Prix - his first win in over five years. In this picture, Lewis Hamilton of Mercedes and Ferrari's Finnish driver Raikkonen attend a press conference ahead of the Singapore Formula One Grand Prix at the Marina Bay Street Circuit in Singapore, Sept. 13, 2018. ROSLAN RAHMAN/AFP/Getty Images

Lewis Hamilton said Kimi Raikkonen’s win at the United States Grand Prix on Sunday showed him that he was not at the peak of his powers and there was still room for improvement before he called time on his F1 career.

The Mercedes driver is on the verge of winning his fifth F1 Drivers’ championship title and the 2018 campaign has been one of Hamilton’s best. It could easily be said that the British racer is the best he has ever been since making his debut in 2007.

The race at the Circuit of the Americas in Austin, Texas, was billed as the race where Hamilton would be crowned champion but it was not to be as a strategy error from the team saw him finish third after starting on pole position. It was Ferrari’s Raikkonen that took the win – his first in over 5 years.

The Finnish racer last won a race at the 2013 Australian Grand Prix and in recent years, many have questioned his motivation after failing to challenge his teammates. Raikkonen is also the oldest driver on the grid, having celebrated his 39th birthday in the week leading up to the race in Austin.

The Finn will leave Ferrari at the end of the season. While many expected him to retire, he decided to continue and signed a two-year deal with Sauber which will ensure he is behind a wheel of an F1 car when he turns 41 in 2020.

Hamilton was mighty impressed and revealed that Raikkonen’s success showed one could continue to improve in the sport, but for a moment the Briton was confused about the Finn’s age. He was also offered an invite to join the Ferrari driver’s 40th birthday celebrations next year.

"I think Kimi's given me a lot of confidence that I can keep getting better," Hamilton said during the post-race press conference, as per Sky Sports. "39," Raikkonen interjected after hearing Hamilton’s confusion about his age. "Next year 40, so I'll invite you to the party."

"Hope I get an invite for the 40th," Hamilton added. "We can call," the Ferrari driver responded.

Hamilton finished the U.S. Grand Prix in third place behind Raikkonen and Max Verstappen, which delayed his championship celebrations. He now needs to finish P7 or better in Mexico to win his fifth title. The Mercedes driver admitted he was keen to win in Austin, but was mindful about being in the title race. He decided to take the points on offer rather than risk an incident by racing the two drivers ahead of him.

“Honestly I was trying to win the race but you look at the two guys next to me, they’re not fighting for a championship so I had to be very, very careful how I navigated around them,” Hamilton said, as quoted on Planet F1. “Championships are not won by fighting and making silly mistakes.”