Instead, Kagan, confirmed by the Senate last month as solicitor general, will wait until the fall to make her debut, Justice Department spokeswoman Beverley Lumpkin said Tuesday.

By the time Kagan took up her post, Lumpkin said, most of the cases the court will hear in April already had been assigned.

"I suppose she could have spent the last several weeks doing nothing but preparing, but that's not something she wanted to do. There's a lot to do getting up to speed in the office," Lumpkin said.

The solicitor general typically handles the top cases before the court. The challenge to a provision of the Voting Rights Act, which will be argued April 29, is perhaps this term's highest-profile case.

Kagan has a most impressive resume — former Harvard Law School dean, Clinton White House official and Supreme Court clerk — but she has little courtroom experience.