Transcript for In letter, Pelosi suggests Trump postpone State of the Union

white house to that suggestion from house speaker Nancy Pelosi that president trump postpone his state of the union address. But this question tonight, does she have the power to make that happen? Mary Bruce on the hill. Reporter: In a bold power play, the speaker of the house tonight is sending a pointed message to president trump, suggest nothing deal to reopen the government, no state of the union. Madam speaker, is the 29th off the calendar as of now? I'm waiting to hear back from the president. Reporter: In her surprise letter, the speaker writing -- "Dear Mr. President, sadly, given the security concerns, and unless government reopens this week, I suggest that we work together to determine another suitable date." Pelosi's other suggest, "Consider delivering your state of the union address in writing." Mr. Speaker! The president of the united States! Reporter: Postponing the annual address would deny the president a powerful platform to make the case for his border wall. Still, the speaker insists this isn't about politics, but a matter of security. With the secret service and department of homeland security suffering from the shutdown. This is a housekeeping matter in the congress of the United States so we can honor the responsibility of the invitation we extended to the president. He can make it from the oval office. Reporter: Tonight, house Republican leader Kevin Mccarthy calls Pelosi's move "Unbecoming of a speaker." Homeland security secretary kirstjen Nielsen tweeting, "The department of homeland security and U.S. Secret service are fully prepared to support and secure the state of the union." And tonight, no word yet from president trump. So, let's get to Mary, live up on the hill again tonight for us. Mary, bottom line, does the speaker really have the power to disinvite the president from the state of the union? Reporter: Yes, David. The speaker of the house does have the power to block the president from delivering the state of the union from the house chamber, but he could deliver it elsewhere, possibly even from the Republican controlled senate. And tonight, we're told Republicans are weighing their options. David? Mary Bruce with us again tonight. Thank you, Mary.

This transcript has been automatically generated and may not be 100% accurate.