House Speaker Nancy Pelosi on Wednesday called upon lawmakers to back a resolution to halt the national emergency declared by US President Donald Trump to fund a wall on the southern border with Mexico.
Trump announced the emergency in order to bypass Congress, which approved only a quarter of the USD 5.6 billion he wanted for the wall in a spending bill.
Sixteen states earlier this week sued over the declaration, but the Trump administration has continued with plans to pull together around a further USD 6.6 billion in federal funding, mostly from the Department of Defense.
Texas congressman Joaquin Castro had last week vowed to introduce a resolution to terminate the president's move.
Lawmakers have until 3:00 pm (2000 GMT) on Thursday to co-sponsor it, before it is formally introduced on Friday.
"I write to invite all Members of Congress to cosponsor Congressman Joaquin Castro's privileged resolution," Pelosi said in a letter to Democrats and Republicans late Wednesday."