By Natascha Divac

FRANKFURT--Claudia Buch, the vice president of Germany's Bundesbank, has warned of the consequences of a Greek exit from the eurozone, saying it would represent "a first-time revocation of a European integration step," and change the character of the currency union, German daily Boersen-Zeitung quotes her as saying in its Saturday edition.

"The discussion around Grexit is...tiring," Mrs. Buch is quoted as saying. The recent negotiations "set the course for Greece to remain within the euro," and Mrs. Buch is "cautiously optimistic" that Greece will succeed in achieving a turnaround.

German Finance Minister Wolfgang Schaeuble had floated the idea about a temporary Greek exit from the eurozone last month. Despite leaders reaching an agreement to give Greece a third bailout under certain conditions, Mr. Schaeuble continued to cast doubt on Greece's eurozone future.

Mrs. Buch was skeptical, however, regarding explicit debt relief for Athens, Boersen Zeitung reports.

"Debt relief between member states of the currency union isn't possible, as it would hurt the no bail-out principle," she is quoted as saying.

She also doubts that the program of the eurozone bailout fund, known as the European Stability Mechanism, is the right way to help Athens. But in Germany, it is up to the parliament to decide whether Athens qualifies for an ESM program, she is reported as saying.

Write to Natascha Divac at natascha.divac@wsj.com