US President Donald Trump says he will deliver a speech to Congress next week, despite calls from top Democrats for it to be postponed over security risks.
Mr Trump insists the State of the Union will happen on 29 January since House Speaker Nancy Pelosi already invited him to address Congress this month.
Mrs Pelosi said that was before the shutdown dragged into day 33.
She shot back in a second letter that the lower chamber would not authorise the address before the shutdown ends.
The president told reporters on Wednesday that Mrs Pelosi had cancelled the speech "because she doesn't want to hear the truth".
"She's afraid of the truth," Mr Trump said. "She doesn't want the American public to see what's going on."
Democrats have argued that with so many federal employees furloughed - temporarily laid off - or working without pay, the high-profile State of the Union address, which involves both chambers of Congress and the president, would not be logistically feasible.
But Mr Trump has denied that there were any security concerns posed by the ongoing partial shutdown.
What has Pelosi said?
The Speaker, who is the third most powerful politician in the US, had invited Mr Trump at the start of January to address Congress on the agreed-upon date of 29 January.
"At that time, there was no thought that the government would still be shut down," Mrs Pelosi said in her letter on Wednesday.
"I am writing to inform you that the House of Representatives will not consider a concurrent resolution authorising the President's State of the Union address in the House Chamber until government has opened."
"Again, I look forward to welcoming you to the House on a mutually agreeable date for this address when government has been opened."
Mrs Pelosi had first asked for the State of the Union, a keynote agenda-setting speech by the president, to be delayed on 16 January, citing an unfunded Secret Service and Department of Homeland Security.
In retaliation, Mr Trump on Friday denied Mrs Pelosi use of military airplanes on a trip to Brussels and Afghanistan - less than an hour before her flight was due to depart.
He asked her to stay to negotiate an end to the partial US government shutdown.
Why is the US government partially shut down?
A row between the Republican president and Democrats over border security has led to the longest government shutdown in US history.
Mr Trump is demanding $5.7bn (£4.4bn) of congressional funding to build a wall on the US-Mexico border, but newly empowered Democrats have refused.
Some 800,000 federal employees have been going unpaid since 22 December as a result of the shutdown.
Donald Trump says he wants to deliver his State of the Union speech "on time, on schedule and on location". He can accomplish the first two without difficulty.