WASHINGTON, D.C. — President Donald Trump will address the nation on Tuesday night and travel on Thursday to the U.S.-Mexico border to press his case for a wall there, as a government funding impasse over the issue forced a partial federal shutdown into a third week with no end in sight.

The president tweeted on Monday that he would speak on national television at 6 p.m. Pacific Time on Tuesday “on the Humanitarian and National Security crisis on our Southern Border.” That followed an earlier tweet from press secretary Sarah Huckabee Sanders that Trump would travel to the border two days later, suggesting the White House sees no end to the impasse for most of this week.

Sanders said details about where Trump would go would be announced soon.

Democrats and other critics, as well as some Republicans, have disputed Trump’s characterizations of conditions at the border as a national security crisis. His and Sanders’ claims that 4,000 terrorists have entered the country have been debunked by the State Department, which reported that no known terrorist had entered from Mexico.

Even as the pain of the shutdown is being increasingly felt, including at the nation’s airports and national parks and by federal employees working without pay, Trump emphasized again on Sunday that unless Democrats agreed to his demand for $5.7 billion to build a wall, he was prepared for the standoff “to go on for a long time.”

“There’s not going to be any bend right here,” he told reporters at the White House.

Trump also said that if the impasse persisted, he might declare a national emergency to bypass Congress and use existing funds for the military to construct a wall.

After stoking fears of a migrant caravan in the run-up to the November elections, the president has continued to depict a crisis on the border to pressure Democrats to accede to his demand.

Democrats have resisted and continue to try to pressure him to reopen the government before they will negotiate further on border security funding.

On Thursday, House Democrats approved two bills to reopen the government, one of which included $1.3 billion in border security funding. Senate Republicans, however, refused to take up the bills without Trump’s support, having passed similar bills unanimously last month only to have him oppose the legislation — provoking the shutdown on Dec. 22.

This week, House Democrats plan to pass similar bills, ratcheting up pressure on the Republican-controlled Senate and Trump.