Vice President Mike Pence and other Trump administration officials are calling on senators to back President Donald Trump's emergency declaration to build his southern border wall, citing an increase in illegal border crossings in recent months.

Vice President Mike Pence on Wednesday criticized lawmakers from both parties who plan to support a resolution to block the president's emergency declaration.

"A vote against the president's emergency declaration is a vote against border security," Pence said in a speech at the Latino Coalition Legislative Summit in Washington. "A vote against the president's emergency declaration is a vote to deny the real humanitarian and security crisis at our southern border. And so we call on every member of the United States Senate to set politics aside, stand up for border security, stand with this president and put the safety and security of the American people first."

Democrats and a handful of Republicans in the Senate have vowed to opposed Trump's declaration, with many citing concerns that the move seeks to go around the lawmakers' constitutional spending authority.

Senate Majority Leader Mitch McConnell, R-Ky., conceded Monday that he believes the chamber will support a resolution to end the national emergency in a vote this month, which would prompt a presidential veto that lawmakers likely would not be able to override.

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The Senate is expected to vote on the resolution — which the House passed last week in a 245-182 vote — by March 15, before the Senate’s next recess. Sen. Rand Paul of Kentucky last weekend became the fourth Senate Republican to say that he planned to vote for the resolution, which would ensure the measure was likely pass the GOP-controlled Senate. Susan Collins of Maine, Thom Tillis of North Carolina and Lisa Murkowski of Alaska also plan to support the measure.

Pence and other administration officials, including Homeland Security secretary Kirstjen Nielsen, have cited an increase in illegal border crossings as a reason for lawmakers to support the declaration.

At a congressional hearing on Wednesday, Nielsen urged lawmakers to address what she called a “humanitarian catastrophe” at the border. The secretary, who privately briefed the president and lawmakers on border security this week, scolded Democrats for calling Trump's border wall push a "manufactured crisis."

"This is not a manufactured crisis," Nielsen said. "This is truly an emergency."

Trump made the declaration last month after Congress passed a bipartisan spending bill without the $5.7 billion he had demanded for a southern border wall, but with some money for fencing.

In an appearance on Fox News on Wednesday, White House press secretary Sarah Sanders also denounced lawmakers, particularly the Senate Republicans, who plan to vote to block Trump's declaration.

"Look, my message to that group is to do your job," Sanders said. "If you had done what you were elected to do on the front end, then the president wouldn't have to fix this problem on his own through a national emergency. The president tried multiple times to get Congress to work with him, to address the crisis, they failed to do so. And now the president has to do what is absolutely necessary and what is right and that is to declare a national emergency and fix the crisis at the border."

The number of undocumented immigrants crossing the southern border last month was the highest total for February in 12 years, according to statistics released by Customs and Border Protection on Tuesday.

In 28 days, about 76,000 immigrants without the needed documentation to enter the U.S. either presented themselves at legal ports of entry or were apprehended by Border Patrol between ports of entry.

It is the highest total for February since 2007, Department of Homeland Security officials said at a press conference Tuesday. It is also the highest single month total since Trump was elected in November 2016. Crossings hit nearly 67,000 in October 2016, just before Trump's election.

Still, February did not set an overall record for border traffic. Before 2008, monthly border crossings were consistently over 100,000, and were higher than 200,000 per month in 2000.