"Identical companion legislation to the House resolution will soon be introduced in the Senate," Schumer said in a statement. 
 
House Democrats, with the backing of Speaker Nancy PelosiNancy Patricia D'Alesandro PelosiHistory teaches that Nancy Pelosi is right about impeachment The politics and practicalities of impeachment The Hill's Morning Report - Dems contemplate big election and court reforms MORE (D-Calif.), are expected to file their resolution as soon as Friday. 
 
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The Senate, which convened for roughly a minute earlier Thursday, is out of town until Monday afternoon, making that day the earliest Democrats could file a resolution in the upper chamber. 
 
Trump announced last Friday that he would declare a national emergency to construct the wall after Congress included only $1.375 billion for physical barriers along the border in a government funding bill — well below the $5.7 billion the president requested. 
 
A resolution blocking Trump's move only needs a simple majority in both chambers to get to the president's desk, where White House officials have suggested he would use his first veto since taking over the Oval Office. 
 
Democrats, and some Republicans, argue that Trump is violating the separation of powers by using an emergency declaration to leapfrog Congress after not getting the votes to get the amount of wall funding that he wants. 
 
“If the president’s emergency declaration prevails, it will fundamentally change the balance of powers in a way our country’s founders never envisioned. That should be a serious wake up call to senators in both parties who believe in the constitutional responsibility of Congress to limit an overreaching executive," Schumer said. 

"This issue transcends partisan politics, and I urge all senators — Democrats and Republicans — to support this resolution to terminate the president’s emergency declaration when it comes up for a vote in the Senate," he added.

Democrats have also seized on Trump's comments from Friday, when he said he didn't "need" to declare an emergency at the border but did so because he wanted to build the wall faster. 
 
If all 47 Democrats vote for the resolution to block Trump's emergency declaration, they will still need to flip four Republican senators. 
 
 
"I don't know what the vote situation will be in the Senate, nor do I know exactly what that resolution will say, but it is a privileged matter. That means that it will come before the Senate for a vote, and if it's a clean disapproval resolution, I will support it," she told reporters in Maine on Wednesday. 
 
Several other Republican senators have raised concerns about Trump's actions but stopped short of saying how they will vote. 

Sen. Lisa MurkowskiLisa Ann MurkowskiJuan Williams: Don't rule out impeaching Trump The 25 Republicans who defied Trump on emergency declaration Overnight Defense: Senate rejects border emergency in rebuke to Trump | Acting Pentagon chief grilled on wall funding | Warren confronts chief over war fund budget MORE (R-Alaska) said late last week that she didn’t “think that this is a matter that should be declared a national emergency.”

And Sen. Lamar AlexanderAndrew (Lamar) Lamar AlexanderWhite House proposes limits on student loan borrowing as part of higher education reforms The 25 Republicans who defied Trump on emergency declaration Trump issues first veto, warning of 'reckless' resolution MORE (R-Tenn.) said in a statement after Trump's announcement that the decision was "unwise" because of the precedent it set for future presidents.

"It is inconsistent with the U.S. Constitution because after the American Revolution against a king, our founders chose not to create a chief executive with the power to tax the people and spend their money any way he chooses," he said. "The Constitution gives that authority exclusively to a Congress elected by the people.”