UPDATED with Kennedy Center Honors, NBC football and Trump: President Obama will be late for the ceremony for tonight’s Kennedy Center Honors, though he will host a pre-ceremony reception for honorees at the White House as planned. Earlier, it was unclear whether the president could show up for the ceremony. The Kennedy Center for the Performing Arts also confirmed that First Lady Michelle Obama will attend the ceremony. Also, NBC confirmed that the network will air the president’s address, breaking away from the network’s Sunday Night Football pre-game coverage, then rejoin the game or kickoff immediately following the speech.

Meanwhile, Donald Trump says he’ll live-tweet during Obama’s address.

UPDATED with additional details: President Obama will make a rare address from the Oval Office Sunday night in the wake of San Bernardino’s slaying of 14 people and wounding of 21 other by a pair of heavily armed shooters on Dec. 2. The White House said the President will address the ongoing investigation into the San Bernardino murders as well as the nation’s overall battle against the threat of terrorism. The address is scheduled to begin at 8PM ET/5PM PT tonight.

The White House first contacted the networks Friday about Obama’s plans, but did not explain why he wanted the time on Sunday in particular, rather than that night, or any time on Saturday, according to people familiar with the situation. On Sunday, HUT levels are higher than those other nights. And, waiting until Sunday night also gave the Obama administration the opportunity to warm the room, as it were, with appearances on the broadcast networks’ Sunday Beltway shows. Attorney General Loretta Lynch, for instance, went on NBC’s Meet the Press this morning to say Obama will use the air time to urge Americans not to “give in to fear.” Making her first Sunday Beltway show appearance as attorney general, Lynch forecast “you may hear him call on Congress to review measures and take action as well. But I think what you’re going to hear the president say is to call on the American people to pull out the best in themselves and not give into fear at this time.”

If so, Obama’s appearance will not break news, this being the same message he and his administration were delivering on Friday afternoon. Even so, the broadcast networks scrambled to shuffle their Sunday night lineups to accommodate. CBS will cover Obama’s speech live as a special report, which will likely air during its 60 Minutes broadcast, given the high likelihood the newsmag will be delayed by a football overrun. Scott Pelley will anchor the CBS News special report live on the East Coast.

CBS also is working on plans for tonight’s reconfigured Kennedy Center Honors ceremony. POTUS usually sits in the balcony with the honorees at the Kennedy Center theater during the ceremony, which can take about four hours; Obama may not be able to attend due to tonight’s address, but it’s unclear who would go in his place, whether First Lady Michelle Obama will attend alone, or if the president might show up later in the ceremony. Obama does plan to participate in the annual reception for the honorees at the White House prior to the ceremony, insiders say.

NBC News’s special report will be anchored by Lester Holt in Los Angeles with Chuck Todd joining from the White House. A Fox News feed is being made available to Fox broadcast stations and The Simpsons and Brooklyn Nine-Nine will be pushed back at least 15 minutes. ABC likewise will delay the fall finale of Once Upon A Time by 15 minutes, with George Stephanopoulos anchoring the news report.

The White House said Obama’s address to the nation will run from 8-8:30PM ET/5-5:30PM PT.

Sunday’s address will mark only the third time this President has delivered a speech from the Oval Office. In June 2010, he outlined a plan to deal with the Deepwater Horizon oil spill and in August the same year he announced the end of combat operations in Iraq.