Democratic leaders in Congress condemned President Donald Trump on Friday as he announced a national emergency declaration that gives him the power to build a long-promised border wall with money lawmakers never earmarked for that purpose.

House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer claimed in a joint statement that there is no 'crisis' on the U.S.-Mexico border, and threatened to defend the spending power of Congress with every tool at their command.

'The President's unlawful declaration over a crisis that does not exist does great violence to our Constitution and makes America less safe, stealing from urgently needed defense funds for the security of our military and our nation,' they said.

'This is plainly a power grab by a disappointed President, who has gone outside the bounds of the law to try to get what he failed to achieve in the constitutional legislative process.'

House Speaker Nancy Pelosi said Friday that President Donald Trump exceeded his authority in declaring a 'national emergency' on the southern U.S. border

In a joint statement with Pelosi, Senate Minority Leader Chuck Schumer said congressional Democrats will go after Trump in the courts and try to block him on Capitol Hill

The president said Friday in a Rose Garden speech that he had signed a national emergency declaration; under a decades-old federal law, that gives him the power to repurpose previously budgeted money as he sees fit

Trump said in a Rose Garden press event that he would leverage about $6.5 billion in existing Defense Department and other funds, along with $1.4 billion Congress appropriated for his wall this week.

White House officials said earlier in the day on a conference call that the money would allow for the construction of at least 234 miles of steel bollard walls.

The Democratic National Committee bolstered the case for opposition following Trump's speech, sending reporters a video clip of Trump conceding that his emergency declaration isn't the only path to fulfilling his signature campaign promise.

'On the wall, they skimped,' he said Friday of Congress's decision to give him less than one-quarter of the $5.7 billion he had asked for. 'So I did – I was successful in that sense.'

'But I want to do it faster,' he explained in the Rose Garden. 'I could do the wall over a longer period of time. I didn't need to do this. But I'd rather do it much faster. And I don't have to do it for the election. I have already done a lot of wall for the election, 2020.'

Pelosi and Schumer said the moves 'clearly violate the Congress's exclusive power of the purse, which our Founders enshrined in the Constitution. The Congress will defend our constitutional authorities in the Congress, in the Courts, and in the public, using every remedy available.'

They claimed that if Trump is permitted to tilt the balance of power toward the Executive Branch of government, it 'would fundamentally alter the balance of powers, inconsistent with our Founders' vision.'

'The President is not above the law. The Congress cannot let the President shred the Constitution.'

White House Press Secretary Sarah Sanders tweeted a photo of Trump signing the emergency declaration, a moment that set off a new level of acrimony between Democrats and Republicans

More than 50 previous presidential emergency declarations have survived sporadic complaints from Congress in the past, including a dozen by President Barack Obama. The U.S. Supreme Court has never invalidated one.

House Democrats began a push Friday to call for a Joint Resolution, using votes in the House and Senate, to override the president. It's a move permitted under the National Emergencies Act, a post-Watergate law that Trump used on Friday.

Trumping Trump, however, would require supermajorities in both halves of Congress – an impossibly tall order.

'We call upon our Republican colleagues to join us to defend the Constitution,' Schumer and Pelosi said Friday, likely referring to a resolution introduced by Reps. Joaquin Castro and Alexandria Ocasio-Cortez.

The path to challenge Trump in federal court is more direct and better understood, including by the president himself.

He complained Friday that Democrats will use the liberal Ninth Circuit courts to attack his decision as an extra-constitutional abuse, despite the relative commonality of emergency declarations since the 1976 enactment of the law permitting them.

'I expect to be sued. I shouldn't be sued,' he said. 'Very rarely do you get sued when you do [a] national emergency.'

'We have an invasion of drugs and criminals coming into our country that we stop but it is very hard to stop,' he said, predicting the impact of miles of new border walls.

'With a wall it would be very easy. So I think that we will be very successful in court.'