President Trump on Wednesday implored Senate Republicans to “STAY UNITED!” and vote for his wall on the southern border, dismissing arguments raised to support blocking his national emergency declaration.

“Senate Republicans are not voting on constitutionality or precedent, they are voting on desperately needed Border Security & the Wall,” Trump posted on his Twitter page. “Our Country is being invaded with Drugs, Human Traffickers, & Criminals of all shapes and sizes. That’s what this vote is all about. STAY UNITED!”

The Democrat-controlled House voted last month to block Trump’s emergency declaration, a move the White House says would allow the president to divert money from the Pentagon construction fund for barrier construction.

Senate Majority Leader Mitch McConnell said his chamber will vote on the resolution before lawmakers go on recess on March 15, but he said there aren’t enough votes to pass it.

Four Republicans have announced that they will vote against it: Sens. Rand Paul of Kentucky, Thom Tillis of North Carolina, Susan Collins of Maine and Lisa Murkowski of Alaska.

Republicans hold a 53-47 majority.

Opponents claim the declaration violates Congress’ constitutional right to appropriate funds.

They also raise the possibility that if Trump prevails, Democratic presidents in the future could also sidestep Congress and declare emergencies on issues like climate change or gun control.

If the Senate blocks the declaration, Trump would have to issue his first presidential veto.

It’s unlikely Congress has the two-thirds majority votes needed to override it.

Trump declared a national emergency last month. The wall was a signature issue of his presidential campaign.

The declaration came after Congress refused to authorize the $5.7 billion in funds Trump demanded for the barrier, appropriating only $1.375 billion.