Hamburg have tabled a 7 million euro ($9m) bid for FC Basel's teenage Swiss international midfielder Granit Xhaka, according to a report in German daily Bild on Thursday.
"Hamburg have made a concrete offer for Xhaka," Basel vice-president Bernhard Heussler told Swiss newspaper Blick.
The offer has reportedly been rejected by the Swiss champions, who are due to face Bayern Munich in the Champions League last 16 next month.
Xhaka, 19, has previously stated that playing in the Bundesliga would be "a dream for me" and described Hamburg as "a great club".
"My plan is to play for Basel until the summer," said Xhaka. "But if my club receives a good offer, we'll have to talk about it together."
Xhaka is under contract with Basel until 2015.
Currently 13th in the Bundesliga, Hamburg are coached by Thorsten Fink, who was in charge of the first team at Basel until October.