"We have long-term relationships with both our drivers," a Mercedes spokesman said, without commenting on a report that the German had signed a new deal keeping him at Mercedes for at least another two years after 2014.
Rosberg, son of 1982 world champion Keke, joined Mercedes from Williams in 2010.
At the end of 2011 the team announced he had signed a "multi-year contract extension to include the 2013 season and beyond".
It had been assumed that the 28-year-old's current contract would expire at the end of this year although there has been regular speculation about an extension in recent months.
Rosberg won the season-opening race in Australia and has finished the last four grands prix as runner-up to Hamilton, who is in his second year at the team after replacing retired seven times champion Michael Schumacher.
Britain's Hamilton leads Rosberg in the championship by three points ahead of Sunday's Monaco Grand Prix, the sixth race of the year which the German won from pole position in 2013.
Rosberg has won four races for Mercedes with his first in China in 2012.
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