US President Donald Trump says he will not deliver his annual State of the Union speech until after the government shutdown is over.
On Wednesday House Speaker Nancy Pelosi withdrew an invitation for him to address Congress, saying government services should fully reopen first.
The shutdown has left 800,000 federal staff without pay since 22 December.
Mr Trump wants $5.7bn (£4.4bn) to build a wall on the US-Mexico border, but newly empowered Democrats have refused.
The row over border security has led to the longest government shutdown in US history.
What did Mr Trump say?
Having initially said the speech should be “on time, on schedule, and very importantly, on location”, he conceded overnight that he could not deliver on his pledge.
He acknowledged Ms Pelosi’s refusal to allow Congress to host the State of the Union address until the shutdown – now in its 34th day – had been resolved.
“This is her prerogative,” he said.
Ms Pelosi responded with her own tweet saying she hoped Mr Trump would back a bill passed by the House of Representatives to fund the agencies affected by the shutdown.
“Please accept this proposal so we can re-open government, repay our federal workers and then negotiate our differences,” she said.
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.
He also rejected suggestions that he could deliver the speech from the White House or another location.
What is Pelosi’s position?
In early January, the House speaker, the third most powerful politician in the US, had invited Mr Trump to address Congress on the agreed-upon date of the 29th.
“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, an 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 last week denied Mrs Pelosi the use of military aircraft 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.
Games of chicken
Donald Trump said he wanted to deliver his State of the Union speech “on time, on schedule and on location”. He could have accomplished the first two without difficulty.
The Constitution is silent on how the president “from time to time” must communicate with Congress.
The “location”, however, was to prove tricky. Ms Pelosi has near-total control over her chamber of Congress.
While she did invite Mr Trump to speak earlier this month, the legislative action to allow the president to give his joint address has yet to be implemented.
Mrs Pelosi has said she’s not budging until the government reopens – and in this particular case, her word is final.
All this set up a game of chicken over a speech within the game of chicken over the shutdown. For the moment, polls show Americans holding the president responsible for the impasse.
But the fallout from this unprecedented State of the Union drama is unpredictable, to say the least.