Lewis Hamilton respects his new battle with Sebastian Vettel more than his acrimonious former scrap with now-retired world champion Nico Rosberg, Niki Lauda has suggested.

Ever since Rosberg decided to quit F1, Hamilton has been giving hints that he does not fully acknowledge the retired German's talent.

"Well, this is the first time he has won in 18 years, so it's not a surprise that he decided to stop," the Briton said just after Rosberg made his announcement late last year.

Now, with Hamilton and Ferrari's Vettel tied after two races in 2017, Hamilton suggests that he much prefers battling against the German wearing red.

"The scenario I'm in right now - fighting against a four-time world champion - the ultimate fighter always wants to go up against the best battle that he can have," he said.

"Because then when you come out on top, it's just so much more satisfying."

Lauda told Germany's Sky: "This is, of course, a shot against Nico.

"Now he fights against someone who has won several world championship titles, of course he plays this up and enjoys it. That's his right.

"Maybe I'm wrong, but I believe this (Vettel battle) has freed him."

Indeed, he suggested that after years of intra-team acrimony with Rosberg, Hamilton is now relishing a fight with another driver and a better atmosphere within Mercedes.

"Lewis is getting along really well with Valtteri - the two harmonise and motivate each other," said Lauda.

Hamilton and Vettel share the lead at the top of the drivers' rankings with 43 points apiece.