President Donald Trump vowed again Tuesday to shut down the federal government in September if the Democrats don't give him the $25 billion for his border wall, declaring "I don't care what the political ramifications are."

"Our immigration laws and border security have been a complete and total disaster for decades — and there is no way that the Democrats will allow it to be fixed without a government shutdown," the president said in a pair of tweets:

I don’t care what the political ramifications are, our immigration laws and border security have been a complete and total disaster for decades, and there is no way that the Democrats will allow it to be fixed without a Government Shutdown... — Donald J. Trump (@realDonaldTrump) July 31, 2018

...Border Security is National Security, and National Security is the long-term viability of our Country. A Government Shutdown is a very small price to pay for a safe and Prosperous America! — Donald J. Trump (@realDonaldTrump) July 31, 2018

"A government shutdown is a very small price to pay for a safe and Prosperous America," Trump said.

The president first threatened a shutdown on Sunday, saying that Democrats needed to back his immigration reform package, which included the wall on the U.S. border with Mexico.

I would be willing to “shut down” government if the Democrats do not give us the votes for Border Security, which includes the Wall! Must get rid of Lottery, Catch & Release etc. and finally go to system of Immigration based on MERIT! We need great people coming into our Country! — Donald J. Trump (@realDonaldTrump) July 29, 2018

Trump caught Republican leaders off-guard — and House Speaker Paul Ryan of Wisconsin and Senate Majority Leader Mitch McConnell of Kentucky said Monday that they opposed a shutdown.

McConnell said senators would put the finishing touches on a federal spending package this week as the Sept. 30 budget deadline neared.

In addition, Alabama Republican Sen. Richard Shelby opposed a shutdown, telling reporters Monday: "I don't think anybody wins on that.

"I think that's a no-win for both parties," he said. "I think Democrats will tell you that, too."

Trump also promised to shut down the government over the wall issue at a Monday news conference with Italian Prime Minister Giuseppe Conte.

"If we don't get border security, after many, many years of talk within the United States, I would have no problem doing a shutdown," Trump said at the joint news conference. "It's time we had proper border security.

"We're the laughing stock of the world," the president said. "We have the worst immigration laws anywhere in the world."

However, Trump that said the $25 billion figure for the barrier was not a "red line" and that he "always leaves room for negotiation" with Democrats.

"I have no red line," the president said in response to a reporter's question. "I just want great border security."

The federal government closed twice this year over funding issues: for three days in January over the status of those in the Deferred Action for Childhood Arrivals program, and for nine hours in February, though no services were interrupted.

A 16-day partial federal shutdown in October 2013 cost American taxpayers $1.4 billion.

Other closures occurred in 1995 and 1996.