U.S. Vice President Joe Biden apologized to Prime Minister Shinzo Abe on Wednesday for "causing trouble," after documents released last week detailed alleged spying by the U.S. National Security Agency on the government in Tokyo, a top Japanese official said.

Chief Cabinet Secretary Yoshihide Suga said the phone conversation between Biden and Abe came about at Washington's request.

Suga declined to comment on whether Biden admitted the U.S. had spied on Japanese officials and companies over a period that started in 2006, as alleged in documents released last week by anti-secrecy group WiliLeaks.