WASHINGTON — The Obama administration has written 275 briefing papers for the incoming Trump administration: nearly 1,000 pages of classified material on North Korea’s nuclear program, the military campaign against the Islamic State, tensions in the South China Sea, and every other kind of threat the new team could face in its first weeks in office.

Nobody in the current administration knows whether anyone in the next has read any of it.

Less than three days before President Obama turns the keys to the White House, and the nuclear codes, over to President-elect Donald J. Trump, Mr. Trump’s transition staff has barely engaged with the National Security Council below the most senior levels. His designated national security adviser, Lt. Gen. Michael T. Flynn, has met four times with his Obama counterpart, Susan E. Rice, most recently on Tuesday afternoon.

But the chronic upheaval in Mr. Trump’s transition, a delay in appointing senior National Security Council staff members, and a dearth of people with security clearances have deprived the Trump team of weeks of prep work on some of the most complex national security issues facing the country.

“We really wanted to make sure there was nothing a new team needed to know that we hadn’t told them,” Ms. Rice said in an interview. “It took them more time than we expected for them to be ready to engage with us.” Now, she added, “we’re racing to make up lost time.”