The pair had a terse exchange in the press conference immediately after qualifying in Barcelona.
Rosberg had outperformed his Mercedes team-mate Hamilton in practice, but had to play second fiddle as the Briton produced a brilliant lap as time expired to nick pole.
The German, who has watched his British rival win the last three grands prix - finishing second each time - made no attempt to hide his frustration when asked how he felt.
"I'm very disappointed," said Rosberg. "I don't particularly enjoy coming second to Lewis."
Hamilton shot back: "We knew that already."
"Yeah, well, there we go, I'm just answering the question," Rosberg responded with a strained smile.
Nico Rosberg and Lewis Hamilton really look like they're on the same team...but not on this planet! pic.twitter.com/fZ1nKWlMMQ
— Laurence McBeth (@LaurenceMcBeth) May 10, 2014
The pair enjoyed a cordial relationship during their first season at Mercedes, but their rivalry has grown during a 2014 season in which the team has completely dominated F1. Hamilton added:
"It's been a tough day. Nico was driving really well and I didn’t know if I was going to be able to get it but I eked out everything I could from the car. Coming here, we didn’t know where everyone was going to be, but to see all the hard work of the team really inspires me."
"In the end, it was a good lap from me so Lewis just did a better job. It's still all to play for tomorrow. I'm a little bit away from optimum but it just takes a good start and I'm in the lead again."
Rosberg won the opening race in Australia as Hamilton retired, but Hamilton has hit back strongly, and Mercedes' refusal to impose team orders has produced some thrilling battles between the pair.
Barring retirements, they are widely expected to finish first and second - in some order - in Sunday's Spanish Grand Prix.
- Sports & Recreation
- Motor Racing
- Lewis Hamilton
- Nico Rosberg