U.S. officials say a news conference with Defense Secretary Chuck Hagel and Afghan President Hamid Karzai is cancelled because of a security threat, but the two men plan to meet privately.

The cancellation comes a day after a suicide bomber on a bicycle struck outside the Afghan Defense Ministry killing nine Afghan civilians and wounding 14 others.

U.S. officials would not provide details on the security concerns. They spoke on condition of anonymity because they weren't authorized to discuss the matter publicly.

Pentagon press secretary George Little said the cancellation was not due to remarks Karzai made earlier suggesting that the Taliban and the U.S. are working in concert to convince Afghans that violence will worsen if most foreign troops leave as planned by the end of next year.