President Donald Trump’s declaration of an emergency on the US-Mexico border looks likely to be dealt a blow by dissident Republican senators.
Several members of the president’s own party are expected to rebel when the Senate votes on Thursday on a proposal to revoke his declaration.
The Democratic-controlled House of Representatives last month backed the measure.
Mr Trump warned he was ready to veto the resolution.
In another tweet he branded Democrats “border deniers”.
“They refuse to see or acknowledge the death, crime, drugs and human trafficking at our southern border,” he said.
The measure to terminate the emergency declaration is expected to pass the Republican-controlled Senate after five Republican members said they would support it.
Those senators are Susan Collins of Maine, Lisa Murkowski of Alaska, Thom Tillis of North Carolina, Mike Lee of Utah and Rand Paul of Kentucky.
However, Congress needs a two-thirds majority of both chambers to override a presidential veto, which is widely viewed as unlikely in this case.
Nevertheless, such a defeat would be another rebuke to the president – a day after the Senate approved a bill to end US support for the Saudi-led coalition in Yemen.