WASHINGTON — During his flight overseas, the Christmas Day airline bombing suspect was flagged by security officials for extra security screening once he landed in Detroit, U.S. officials said today as they prepared to release the clearest look yet at government missteps in the near-catastrophe.

The White House planned to make public a declassified account of how a suspected terrorist slipped through post-Sept. 11 security to board the plane with an explosive. President Barack Obama was to address the nation later today about the findings and recommendations. Obama was also to reveal new steps intended to thwart terrorist attacks, as he promised earlier in the week.

No firings over the December security debacle are expected — for now, at least.

In a statement early today, the Department of Homeland Security said the alleged bomber's potential ties to extremists came up in a routine check of passengers en route to the U.S. from overseas.